Curling is a sport with similarities to bowls and bocce, played on a rectangular sheet of carefully prepared ice by two teams of four players each. Teams alternate turns at sliding heavy, polished granite stones down the ice towards the target area called the house. Two sweepers accompany each rock and use timing equipment and their best judgement along with direction from their other teammates to help direct the stones to their resting place. The complex nature of stone placement and shot selection has led some to refer to curling as "Chess on ice".
The curling sheet is an area of ice 146 feet (45.5 m) in length by 14 feet 2 inches (4.318 m) to 16 feet 5 inches (5.0038 m) in width, carefully prepared to be as close to level as possible. A key part of the preparation is the spraying of water droplets onto the level ice. These water droplets are called pebble. Due to the friction between the stone and pebble, the stone turns to the inside or outside, causing the stone to 'curl'. The amount of curl can change during a game as the pebble wears. The surface of the ice is maintained at a temperature near 23°F (-5°C).
Making and maintaining perfect ice conditions at a curling club is as much an art as a science. Most curling clubs have an ice maker whose main job is to care for the ice. At the major curling championships, ice maintenance is extremely important. Well known professional ice makers Shorty Jenkins, Hans Wuthrich and Dave Merklinger reside in Canada. Large events such as the Brier or other national championships are typically held in an arena which presents a challenge to the ice maker as they must constantly monitor and adjust the ice and air temperatures as well as air humidity levels to ensure a consistent playing surface. It is common for each sheet of ice to have multiple sensors embedded to monitor surface temperature as well as probes set up in the seating area to monitor humidity and in the compressor room to monitor brine supply and return temperatures.
On the sheet, a 12 foot (3.7 m) wide set of concentric rings, called the house, is painted near each end of the rink. The centre of the house is marked by the junction of two lines that divide the house into quarters and is known as the button. The two lines are the centre line, which is drawn lengthwise down the centre of the sheet, and the tee line, drawn 16 feet (4.9 m) from the backboard and parallel to it. Two other lines, the hoglines, are drawn parallel to each backboard and 37 feet (11.3 m) from it.
The rings that surround the button are defined by their diameter as the four-foot, eight-foot, and twelve-foot rings. They are usually distinguished by colour. The inner rings are merely a visual aid for judging which stone is closer to the centre; they do not affect scoring; however, a stone that is not at least touching the outside of the 12-foot ring (i.e. more than 6 feet from the centre) is not in the house and therefore does not score (see below).
Twelve feet behind the button are located the hacks. A hack is a device used to provide traction to the curler making a shot; the curler places the foot he or she will push off with in the hack. On indoor rinks there are usually two fixed hacks, rubber-lined holes, one each side of the centre line with the inside edge no more than three inches (7.6 cm) from the centre line and the front edge on the hack line. A single moveable hack may also be used.
Curling is played between two teams of four curlers each, with team members named for the usual order in which they play. The lead plays first, then the second, the third (or mate), and finally the fourth; the fourth is typically the skip (team captain) but not always. For example, skips Randy Ferbey and Russ Howard throw third and second respectively. The position at which the skip (team captain) throws will be renamed with skip. For example, Randy Ferbey's team will be lead, second, skip, fourth, while Russ Howard's team will be lead, skip, third, fourth.
The lead, or first, throws the team's first two stones of an end, and sweeps for the other team members. Strategically, the lead usually has similar shots from end to end, usually throwing guards or draws.
The Second throws the team's Third and Fourth stones and sweeps for all other players.
Also called the vice-skip, vice or mate, the third throws the team's fifth and sixth stones, and usually sweeps for the second and the lead. The third usually assists the skip in his or her duties. When it is the skip's turn to throw, it is usually the third who holds the broom for the skip.
After each end (round of play), the thirds for both teams must reach an agreement about which team scored and how many points. If there is a disagreement, or uncertainty, the thirds may measure the rocks to see which ones are closer. At this time, only the thirds are allowed in the house. In major tournaments, the scorekeeping is left to an official. Depending on the tradition, when the third's team scores, the third will record it on the score-board.
Depending on the tradition, the third may flip a coin with the opposing third to determine who will have last rock (hammer) advantage at the beginning of a game. The winner of the toss has the option to pick either last rock, or the colour of the rocks they wish to play with. In major tournaments, these decisions are usually made beforehand.
The skip is the captain of the team and determines strategy. Based on the strategy, the skip holds the broom indicating where the player throwing must aim ("calling the shot"). When it is the skip's turn to throw, the vice-skip (usually the third) holds the broom. The skip usually throws the last two rocks of the end, however some teams have the skip throwing in other positions.
The skip rarely does any sweeping, except in the house and behind the tee line. The skip is required to stay out of the playing area when it is the other team's turn, but he is allowed to sweep stones in motion behind the tee line as a result of their shot. (In International rules, the player in charge of the house is the only player allowed to sweep their opponent's stones behind the tee-line. For most of the end that is the skip, but when the skip is throwing the vice-skip takes charge of the house.)
The "fourth" refers to the thrower of the last two stones in each end for a team if that player is not the skip. That is, if the skip does not play last rocks in each end, the last player to throw is known as Fourth.
Except in international or some national and provincial events in Canada and the United States, a team will usually be identified by the last name of the skip. For example, Cassandra Johnson's foursome is known as "Team Johnson," unless they are representing the United States in the World Championships or the Olympics, in which case they would be known as "Team USA".
When curling, players need to wear specially designed shoes. The sole of one shoe has a thin strip of Teflon or another type of smooth surface, called a slider. Inexpensive sliders can be purchased and attached to any shoes by means of an elastic strap. This enables curlers to slide out of the hack when delivering a rock. Left-handed curlers wear this shoe on their right foot, while right-handed curlers wear it on their left. The other shoe has a thin layer of rubber to maximize traction on the ice. Another piece of footwear is the gripper, which can slide on and off the shoe with the slippery surface. This is also usually made of rubber. This piece of equipment is needed when a player is sweeping, and needs traction with both feet.
Casual players may wear running shoes and improvise a slider by applying tape to their off foot.
Broom (brush)The curling broom is used to sweep the ice surface in front of the rock. Aggressive sweeping momentarily melts the ice, which lessens friction, thereby lessening the deceleration of the rock, while straightening the trajectory of the rock. The broom can also be used to clean debris off the ice, although this is often done in vain. The skip will also hold a broom at the opposite end of the rink from the delivering player as a target for the deliverer aim the rock.
In earlier days, brooms were made of corn strands and were similar to household brooms. Brushes were used primarily by elderly curlers as a substitute for corn brooms. Today, brushes have replaced traditional corn brooms at every level of curling, but are universally referred to as brooms. Brooms are also used by some curlers as a balancing aid during delivery of the stone.
Curling stone (rock)
The curling stone, or rock, weighs a maximum of 44 lbs. (19.96 kg). It has a maximum allowable circumference of 36 inches (0.9144 m). A stone may be a maximum of 4.5 inches (11.43 cm) in height not including the handle. The handle is attached to the stone by means of a bolt, which runs vertically through a hole in the center of the stone. The handle allows the rock to be gripped and rotated upon release. When the rock is thrown with the right hand, clockwise rotation is referred to as an in-turn. Counter-clockwise rotation is referred to as an out-turn. The opposites are true if the rock is thrown with the left hand. The handles are coloured to differentiate the rocks belonging to each team. Two popular colours for handles are red and yellow. The handle may be of the 'Eye on the hog' variety for detecting hog line violations.
The bottom of a curling stone is concave. The surface in contact with the ice, known as the running surface, is a circle ¼ to ½ inch (6 to 12 mm) thick. This narrow running surface is where the ice and the stone interact. On properly prepared ice, the rock's path will bend (curl) in the direction the front edge of the rock is turning, especially toward the end of its motion. The degree of curl depends on several factors, including the preparation of the ice and the flattening of common paths to the house during the game. Ice on which the rocks curl well is said to be swingy.
The Scots in particular believe that the best quality curling stones are made from a specific type of granite called "Ailsite", found on the Ailsa Craig, an island off the Ayrshire coast. According to the Scottish Curling Stone Company, Ailsite has very low water absorption which prevents the action of freezing and melting water from eroding the stone. In the past, most curling stones were made from this granite. However, the island is now a wildlife reserve, and is no longer used for quarrying. Because of the particular rarity of Ailsite, costs for curling stones can reach as much as $1500 (USD) for the best stones. Many curling clubs use a lower grade stone that can be upwards of $500. There are also stones which use a disc of ailsite attached to another type of granite to provide the running surface. Very informal neighbourhood curling clubs with limited resources may make cylindrical "curling stones" out of concrete-filled cans. The curling stones used at the 2006 Winter Olympics in Torino were provided by the Garn For granite quarry at the Yr Eifl mountain on the Llyn Peninsula in North-West Wales.
A special handle for stones, called "Eye On The Hog", has recently been developed, which integrates electronics to ensure the stone is released before it crosses the hog line. The handle is coated in metallic paint; the circuitry detects the relative charge of the thrower's hand contact to determine if they are still in contact, and a linear field is established at the hog line to indicate its location to the internal sensor. Lights at the base of the handle indicate whether contact was sustained past the line or not. Not only does this remove the chance for human error (eliminating the game's most frequent cause of controversy), but it means there is no need for hogline officials as well. The downside for the technology is that the equipment currently costs around $650 a piece which multiplies quickly with the amount of rocks and sheets of ice in a tournament. Therefore its use is found mostly in high-level national and international competitions such as the Winter Olympics.
Although the rock is designed to be delivered by players grasping the handle as they slide down the ice, a special "delivery stick" may be used by players incapable of delivering the rock in this fashion. Such a stick is designed to attach to the handle so that it can be released without requiring the player to place a hand on the handle in a crouched position. This allows the game to be played by players with disabilities, as well as those unable to crouch comfortably. According to the Canadian Curling Association Rules of Curling, "The use of a curling aid commonly referred to as a 'delivery stick' which enables the player to deliver a stone without placing a hand on the handle is considered acceptable."
A competitive game usually consists of ten ends. Recreational games are more commonly only eight or even six ends. An end consists of each player from both teams throwing two rocks with the players on each side alternating shots, for a total of sixteen rocks. If the teams are tied at the completion of ten ends an extra end is played to break the tie. If the match is still tied after the extra end, play continues for as many ends as may be required to break the tie. The winner is the team with the highest score after all ends have been completed (see Scoring below).
It is not uncommon at any level for a losing team to terminate the match before all ends are completed if it believes it no longer has a realistic chance of winning. Most competitive tournaments require eight ends to be completed before allowing a losing team to concede in this manner. Competitive games will usually end once the losing team is "run out of rocks" - that is, once it has fewer stones in play and/or available for play than the number of points needed to tie the game in the final end.
In international competition each side is given 73 minutes to complete all of their throws. Each team is also allowed two 60 second timeouts per ten end game. If extra ends are required each team is allowed 10 minutes of playing time to complete their throws and one added 60 second timeout for each extra end.
When throwing the rock, the player must release it before reaching the near hogline (players usually slide while releasing their shots) and it must cross the far hogline; otherwise the rock is removed from play (hogged).
While the first three players throw their rocks, the skip remains at the far end of the ice to guide the players. While the skip is throwing, the third takes this role. Thus, each time a rock is thrown, there is one player throwing the rock, and another player at the far end.
The two remaining players, equipped with brooms, follow the rock and assist in guiding its trajectory by sweeping the ice in front of the rock. Sweeping causes the rock to decrease its curl but travel a greater distance. The sweeping players combine directions from the skip and/or the thrower with their own judgement for the weight of the rock, as well as extremely precise timing, to guide the rock into the appropriate position. Often when giving instructions, the thrower or skip will yell "HARD." They are referring to the amount of pressure the sweepers should use to sweep the ice. In general the sweepers are responsible for instructing the skip in regards to the weight, or speed of the rock, and the skip and the thrower instruct regarding aim. Teams confer between throws to determine where they will attempt to place the next rock.
Delivering the rock
The process of throwing a rock is known as the delivery. While not mandatory, most curlers deliver the rock from sliding out from the hack. When sliding out, one shoe (the one with the non-slippery sole)is positioned against one of the hacks (a position referred to as being in the hacks). For a right-handed curler, this means starting from the left hack, and vice versa for a left-handed curler.
When delivering the rock, it is important to remember that the momentum behind how much weight is applied to the rock depends on how much leg drive the delivery has. It is usually not wise to push the rock with the arm, unless absolutely necessary. When in the hack, one must crouch down with the body lined up and shoulders square with the skip's broom at the other end. While in the hack, one may hold a broom out for balance. Different curlers hold their broom out in many different fashions. The broom is held in the hand opposite from the rock, and should be positioned so that the non-sweeping side of the broom is against the ice. This prevents drag which would be caused by the soft head of the broom dragging against the ice.
Before any delivery, it is important to ensure that the running surface of the rock is clean, and that the area around you is clean as well. This is achieved by wiping the running surface of the rock with either your hand or with the broom, and then cleaning the area around you with the broom. The reason for this is that any dirt in the area or on the bottom of a rock could alter the trajectory of it and ruin the shot. When this happens, this is called a "pick".
After cleaning the rock, the next step is to know what rotation, or turn, to put on the rock. The skip will usually tell the thrower this information. The thrower will then place the handle of the rock generally at either a "two o'clock" or a "ten o'clock" position. When delivering the rock, the thrower will turn the rock from one of these two positions toward the "twelve o'clock" position before releasing it. A rock turned from ten o'clock to twelve will spin clockwise and curl to the right, and a rock turned from two o'clock to twelve will have the opposite effect. A generally desired rate of turn is about two and a half rotations before coming to a rest.
Once the thrower knows the turn to give the rock, the thrower will place the rock in front of his or her toe in the hack. At this point the thrower will then start his or her delivery. This begins by slightly rising from the hack, and moving the rock back to one's toe. This is the beginning of a pendulum movement that will determine the force given to the rock. Some older curlers will actually raise the rock in this backward movement, as this is what they are accustomed to. The forward thrust of the delivery comes next. The thrower moves his or her slider-foot in front of the other foot while keeping the rock ahead of him. The thrower then lunges out from the hack. The more thrust from this lunge, the more power or "weight" the rock will have. When lunging out, the gripper-foot will drag behind the thrower. When lunging out, it is important to push as precisely as possible in the direction of the skip's broom at the other end, so that the "line" of the rock is accurate. The rock should be released before the thrower's momentum wanes at which point the thrower imparts the appropriate curl, keeping in mind the stone should be released before the first hog-line.
The amount of weight given to the rock will also be told to the thrower by the skip at the other end. This usually occurs by the skip tapping the ice with his broom where he or she wants the rock to be delivered. In the case of a take-out or a tap, the skip will tap the rock that he or she wants removed or tapped.
It should also be noted that with a more skilled skip, where he wants the rock to land will not always be the exact place he holds the broom if the skip expects the rock to curl. When the rock is delivered accurately at the broom, it will curl towards where the skip wants it to land.
Curling has also been adapted for play for those that are wheelchair bound, or otherwise unable to throw the rock from the hack. Handicapped curlers may use a special device known as a "curler's cue" or "delivery stick". The cue holds on to the handle of the stone and is then pushed along by the curler. At the end of delivery, the curler pulls back on the cue, which releases it from the stone.
When a rock is delivered, it is important that there be two players following the rock so that they are ready to sweep its path if needed. Sweeping is done for two reasons: to make the rock travel farther, and to make the rock travel straighter (curl less). When sweeping, pressure and speed of the brush head are key in slightly melting the pebbled ice in the path of the rock.
One of the interesting strategy aspects of curling is knowing when to sweep. When swept, a rock will always travel both farther and straighter. In some situations, one of the two is often not desirable (for example, a rock may have too much weight, but needs sweeping to prevent curling into a guard), and the team must decide which is better: getting by the guard but traveling too far, or hitting the guard.
Much of the yelling that goes on during a curling game is the skip calling the line of the shot. The skip evaluates the path of the rock and calls to the sweepers to sweep as necessary to hold the rock straight. The sweepers themselves are responsible for judging the weight of the rock and ensuring the length of travel is correct.
Usually, the two sweepers will be on opposite sides of the rock's path. Grip of the broom is vital - one hand grips the top (non-brush end) of the handle while the other grips the handle close to the head of the broom so that as much pressure as needed may be applied while sweeping, though the precise amount of pressure may vary from relatively light brushing to maximum-pressure scrubbing. It is important to never to touch the rock while sweeping (a rock touched by a sweeper is burned, and the opposing skip may opt to have the rock removed from play).
Sweeping can be done anywhere on the ice up to the "tee-line", as long as it is only for your own team's rock. Once your team's rock crosses the tee-line, only one player may sweep it. Additionally, when an opposing rock crosses the tee-line, one player from your team is allowed to sweep it. This is the only case that a rock may be swept by an opposing team member. In international rules, this player must be the skip, or if the skip is throwing, then the third.
Types of shots
Essentially, there are two kinds of shots in curling, the draw and the takeout. There are many variations of these shots, however. Draws are shots in which the stone is thrown only to reach the house (or in front of the house - when the rock is called a guard), while takeouts are shots designed to remove stones from play. Choosing which shot to play will determine whether the thrower will use an in-turn or out turn, for a right-handed person, the clockwise and counter-clockwise rotation of the stone, respectively. Possible draw shots include guard, raise, come around, and freeze. Takeout shots include peel, hit and roll, chip and hack. For a more complete listing look at the complete list Glossary of curling terms.
Free guard zone
Until four rocks have been played (two from each side), rocks in the free guard zone (those rocks left in the area between the hog and tee lines, excluding the house) may not be removed by an opponent's stone. These are known as guard rocks. If the guard rocks are removed, they are replaced and the opponent's rock is removed from play. This rule is known as the four-rock rule or the free-zone rule; (for a period in Canada, a "three-rock rule" was in place, but that rule has been replaced by the four-rock rule).
This rule, a relatively recent addition to curling, was added in response to a strategy of "peeling" opponents' guard stones (knocking them out of play at an angle that caused the shooter's stone to also roll out of play, leaving no stones on the ice). A team in the lead would often employ this strategy during the game. By knocking all stones out, the opponents could at best score one point (if they had the hammer). Alternatively, the team with the hammer could peel rock after rock, which would blank the end, keeping the last rock advantage for another end. While a sound strategy, this made for an unexciting game.
Last rock (or Hammer)
The last rock in an end is called the hammer. Before the game, teams typically decide who gets the hammer in the first end by coin toss or similar method. (In tournaments, this is typically assigned, giving every team the first-end hammer in half their games.) In all subsequent ends, the hammer belongs to the team that did not score in the preceding end. In the event that neither team scores, the hammer remains with the same team. Naturally, it is easier to score points with the hammer than without; in tournament play, the team with the hammer generally tries to score two or more points. If only one point is possible, the skip will often try to avoid scoring at all in order to retain the hammer until the next end, when two or more points may be possible. This is called a blank end. Scoring without the hammer is commonly referred to as stealing, or a steal, and is much more difficult.
After both teams have delivered eight rocks, the team with the rock closest to the button is awarded one point for each of its own rocks that is closer than the opponent's closest rock. Rocks that are not in the house (further from the center than the outer edge of the 12-foot ring) do not score even if no opponent's rock is closer. A rock is considered in the house if any portion of its edge is over any portion of the 12-foot ring. Since the bottom of the rock is rounded, a rock just barely in the house will not have any actual contact with the ring, which will pass under the rounded edge of the stone, but it still counts. This type of rock is known as a "biter."
The score is marked on a scoreboard, of which there are two types. One is the baseball type scoreboard, which is usually used for televised games. On this scoreboard the ends are marked by columns 1 through 10 (or 11 for the possibility of an extra end to break ties) plus an additional column for the total. Below this are two rows — one for each team. The number of points each team gets in an end is marked this way.
The other form of scoreboard is the one used in most curling clubs (see photo). It is set up in the same way, except the numbered row indicates a team's progress in scoring points rather than marking ends, and it can be found between the rows for the team. The numbers placed are indicative of the end. If the red team scores 3 points in the first end (called a three-ender), then a one (indicating the first end) is placed beside the number three in the red row. If they score two more in the second end, then a two will be placed beside the five in the red row indicating that the red team has five points in total (3+2). This scoreboard works because only one team can get points in an end. However, some confusion can exist if no team gets points in an end. This is called a blank end and the end number usually goes in the furthest column on the right in the row of the team who has the hammer (last rock advantage), or on a special spot for blank ends.
Conceding a game
When a team feels it is impossible or near impossible to win a game, they will usually shake hands with the opposing team to concede defeat. This may occur at any point during the game, but usually happens near the final end. When a game is completed by playing all ends, both teams also shake hands. This is often accompanied by saying "Good game!" Hands are also shaken before the game, accompanied by saying "Good curling!" to the opposing team. In the Winter Olympics, a team may concede after finishing any end during a round-robin game, but can only concede after finishing eight ends during the knockout stages.
Most decisions about rules are left to the skips. However, all scoring disputes are handled by the third, or vice-skip. No players other than the third from each team should be in the house while score is being debated. In tournament play the most frequent circumstance in which a decision has to be made by someone other than the third is the failure of the thirds to agree on which rock is closest to the button. An independent official then measures the distances using a specially designed device that pivots at the center of the button. When no independent officials are available, the thirds measure the distances.
Top curling championships are typically played by all-male or all-female teams. The game is known as mixed curling when played by both men and women. The Canadian Mixed Curling Championship is the highest-level mixed curling competition, in the absence of world championship or Olympic mixed curling events.
Curling is played in many countries including the United States, United Kingdom (especially Scotland), Norway, Sweden, Switzerland, Denmark, Finland and Japan, all of which compete in the world championships.
Curling is particularly popular in Canada. Improvements in ice making and changes in the rules to increase scoring and promote complex strategy have increased the already high popularity of the sport in Canada, and large television audiences watch annual curling telecasts, especially the Scott Tournament Of Hearts (the national championship for women), the Tim Hortons Brier (the national championship for men), and the women's and men's world championships.
Despite the Canadian province of Manitoba's small population, teams from that province have won the Brier more times than teams from any other province. The Tournament of Hearts and the Brier are contested by provincial and territorial champions, and the world championships by national champions.
Curling is the provincial sport of Saskatchewan, home of some of the most famous curlers. Ernie Richardson and his family team dominated Canadian and international curling during the late 1950s and early 1960s and are generally conceded to be the best male curlers of all time. Sandra Schmirler led her team to the first ever gold medal in women's curling in the 1998 Winter Olympics. When she died two years later from cancer, over 15,000 people attended her funeral, and it was broadcast on national television.
An amateur sport
While Canadian bonspiels (tournaments) offer cash prizes, there are no full-time professional curlers. However, some curlers make a considerable portion of their income from curling. Some stay-at-home mothers or house-wives can claim curling as their profession. Still, curling survives as a people's sport, returning to the Winter Olympics in 1998 with men's and women's tournaments after not having been on the official Olympic program since 1924 (that year's curling competition, for men only, was confirmed as official by the IOC in 2006). Because accuracy, strategy, skill, and experience are more valuable in curling than traditional sports virtues of speed, stamina, and strength, most competitive curlers are older than their counterparts in other sports. However, there are many young teams who turn heads, and junior curling is quite popular, with national finals being televised nationwide in Canada.
More so than in many team sports, good sportsmanship is an integral part of curling. For example, celebrating an error by the opposing team, fully acceptable in some sports, is frowned upon in curling. Even at the highest levels of play, a player is expected to "call their own fouls", so to speak, such as alerting the opposing skip if they burned a stone. It is also traditional for the winning team to buy the losing team a drink after the game. (This is in interesting contrast to the game of darts, where the loser traditionally buys the winner a drink by way of congratulations.) This is often referred to as the Spirit of Curling.
As noted above in the game play section, it is not uncommon for a team to concede a curling match after it believes it no longer has a reasonable chance of winning but before all ends are completed. Concession is an honourable act and does not carry the stigma associated with "quitting". To concede a match the losing team removes their curling gloves (if they wear gloves) and offers congratulatory handshakes to the winning team. Thanks and wishes of future good luck are usually exchanged between the teams.
The means of preparation one must take to be competitive in the sport of curling go beyond physical fitness and above-average agility. The competitor must not only be able to have an extensive understanding of classical mechanics with an emphasis on friction, but must be able to apply this knowledge to the playing field. This is a commonly overlooked fact. Curling is an excellent example of the adage "easy to learn, but difficult to master".
By the Numbers
The participants and commentators of curling use various measures to relate information about the behavior of ice and the individual rocks thrown. The ice in the game may be fast or slow. If the ice is fast, a rock will travel farther with a given amount of weight on it. The speed of the ice is measured in seconds. This measure is the amount of time that a draw to the button will spend moving before it comes to a rest. If the ice is slow, the rock will have to have more weight in order to reach the button and would reach the button more quickly. Thus, the speed of the ice (in seconds) is lower than if the ice is fast, in which case the rock would have to be thrown more slowly and would take longer to get there.
Additionally, the weight (speed) of an individual rock can also be measured in seconds. This time is the time the rock takes to cross first one hogline and then the other. If this number is lower, the rock is moving faster, so again low numbers mean more speed. The ice in a match will be somewhat consistent and thus this measure of speed can also be used to measure how far down the ice the rock will travel. Once it is determined that a rock taking (for example) 9 seconds to go from hogline to hogline will stop on the button, the curler can know that if they can match that time with later stones, they can throw stones that will stop near the button.
External LinksWorld Curling Federation
Canadian Curling Association
United States Curling Association