Section 1: Introduction
1.1 Overview and History
Curling is a precision team sport played on a rectangular sheet of prepared ice, in which two teams take turns sliding polished granite stones towards a circular target known as the house. Originating in medieval Scotland during the 16th century, the earliest recorded curling match dates to 1541 in Paisley Abbey. The sport spread throughout Europe and to Canada via Scottish emigrants, where it became deeply embedded in the national sporting culture.
1.2 Governing Body
The World Curling Federation (WCF), headquartered in Perth, Scotland, is the international governing body for curling. Founded in 1966 as the International Curling Federation (ICF) and renamed in 1991, the WCF oversees all international competition and publishes The Rules of Curling and Rules of Competition (latest edition October 2024). The WCF comprises over 60 member associations spanning six continents.
1.3 Olympic Status
Curling appeared as a demonstration sport at the inaugural 1924 Winter Olympics in Chamonix. It returned as a full medal sport at the 1998 Nagano Winter Olympics with Men's and Women's events. Mixed Doubles was added at the 2018 PyeongChang Games. All three disciplines — Men's, Women's, and Mixed Doubles — remain on the Olympic programme.
1.4 The Spirit of Curling
Curling is distinguished by a deeply held tradition of sportsmanship and fair play known as the Spirit of Curling. Players are expected to call their own fouls, congratulate opponents on good shots, and conduct themselves with courtesy. The tradition of Broomstacking — where the winning team buys drinks for the losing team after a match — embodies this ethos. The Spirit of Curling is codified in the WCF rulebook as Rule C1 and is considered the foundation upon which all other rules rest.
Section 2: Equipment
2.1 Curling Stones
Curling stones are made of dense, polished granite. The majority of competition stones are crafted from granite quarried on Ailsa Craig, a small volcanic island off the coast of Ayrshire, Scotland. The two granite types — Blue Hone (extremely rare, used for the running band) and Common Green — are prized for their low water absorption and consistent hardness. Some stones are also sourced from Trefor, Wales.
- Weight: Between 17.24 kg and 19.96 kg (38–44 lb), including handle and bolt (Rule C1(a)).
- Circumference: Maximum 91.44 cm (36 in).
- Height: Minimum 11.43 cm (4.5 in).
- Running band: A narrow, concave annular ring on the bottom of the stone — the only part that contacts the ice. The concavity reduces friction and allows the stone to curl.
- Handle: A gooseneck handle bolted to the top, used to impart rotation (turn) during delivery. Handles are colour-coded to distinguish the two teams (typically red and yellow).
Each team uses 8 stones per game (16 total on the sheet). Stones must not be altered, heated, or treated to change their playing characteristics.
2.2 Brooms and Brushes
- Purpose: Sweeping the ice surface ahead of a moving stone to influence its speed and trajectory.
- Construction: Modern brooms use a carbon fibre or fibreglass shaft with a fabric pad head. Traditional corn brooms are rarely used in competition.
- WCF Approval: All broom heads must comply with WCF specifications. Directional fabric, waterproof coatings, or any material that deposits debris on the ice is prohibited.
- Stabiliser broom: The delivering player uses a broom or stabiliser (delivery stick) in the non-throwing hand for balance during the slide.
2.3 Footwear
- Slider shoe: Worn on the sliding foot (left foot for right-handed deliverers). The sole is coated with Teflon or a similar low-friction material to allow a smooth glide during delivery.
- Gripper shoe: Worn on the hack (push-off) foot. The sole features a high-traction rubber coating for grip on ice.
- Slider guards: Removable rubber covers placed over the slider sole when not delivering, to prevent slipping while sweeping or walking.
2.4 Additional Equipment
- Stopwatch: Used by the skip or vice-skip to time stone speed (split times between hog lines) for weight judgement.
- Measuring device: Used by officials to determine which stone is closest to the tee when it cannot be determined visually.
- Eye on the Hog: Electronic sensor embedded in the stone handle that detects whether the stone was released before the hog line. A green light indicates a valid release; a red light indicates a violation.
Section 3: Playing Area
3.1 Sheet Dimensions
Curling is played on a carefully prepared rectangular sheet of ice with the following dimensions:
- Length: 150 ft (45.72 m) from hack to hack.
- Width: 15 ft 7 in (4.75 m) standard; maximum 16 ft 5 in (5.0 m).
3.2 Key Lines and Markings
- Hack: A rubber foothold embedded in the ice at each end, from which players push off during delivery. The hack is positioned on the centre line, behind the back line.
- Back line: A line drawn across the width of the sheet at each end, positioned 6 ft (1.83 m) behind the tee line. A stone that completely crosses the back line is removed from play.
- Tee line: A line drawn through the centre of the house at each end, perpendicular to the centre line. The intersection of the tee line and centre line is the tee (button).
- Hog line: Located 21 ft (6.40 m) from the tee line at each end. The delivering player must release the stone before the near (delivery-end) hog line. The stone must fully cross the far (playing-end) hog line to remain in play.
- Centre line: Runs the full length of the sheet through the centre of both houses.
- Courtesy line: Located 4 ft (1.22 m) behind each hack. Non-delivering team members must remain behind this line during the opponent's delivery.
3.3 The House (Target)
The house is the circular scoring area at each end of the sheet, consisting of four concentric rings:
- Button: The centre point (tee), marked by the intersection of the tee line and centre line.
- 4-foot ring: 4 ft (1.22 m) diameter.
- 8-foot ring: 8 ft (2.44 m) diameter.
- 12-foot ring: 12 ft (3.66 m) diameter — the outer boundary of the house.
The rings are typically painted in alternating colours (red, white, blue, white from outer to inner). A stone must be touching or within the 12-foot ring to be eligible for scoring.
3.4 Ice Preparation
The ice surface is maintained at approximately −5°C (23°F). After being levelled flat, the ice is pebbled — fine water droplets are sprayed onto the surface and allowed to freeze, creating a textured finish of small bumps. This pebble reduces the contact area between stone and ice, lowering friction and enabling the stone to curl. The pebble is nipped (shaved level) before play to ensure consistency.
3.5 Free Guard Zone
The Free Guard Zone (FGZ) is the area between the hog line and the tee line, excluding the house itself. Stones resting in this zone during the first five deliveries of an end are protected under the Free Guard Zone rule (see Section 5).
Section 4: Players & Officials
4.1 Team Composition (Standard)
A standard curling team consists of four players, each with a designated role and throwing order:
- Lead: Throws the first two stones for the team. Typically responsible for placing guards and early draws. Sweeps for all other teammates.
- Second: Throws stones three and four. Often plays takeouts or draws to build on the lead's positioning. Sweeps for all other teammates.
- Third (Vice-Skip): Throws stones five and six. Acts as skip (strategist/caller) when the skip is delivering. Holds the broom as target for the skip's deliveries. Agrees on scoring with the opposing vice-skip at the end of each end.
- Skip: Throws the last two stones (seven and eight). Directs team strategy, calls the line and weight for each delivery, and positions the broom as the target for teammates. The skip is typically the team's most experienced player.
Teams may register a fifth player (alternate) who can substitute for any position. Once an alternate enters the game, the replaced player cannot return for that game.
4.2 Mixed Doubles Teams
In Mixed Doubles, each team consists of one male and one female player. Each player delivers 5 stones per end (10 total per team across an 8-end game). The first stone of each end must be delivered by the player whose stone is not pre-placed in the house. Players alternate deliveries: one player delivers stones 1 and 5, the other delivers stones 2, 3, and 4 (or vice versa, chosen per end).
4.3 Officials
- Chief Umpire: The senior official responsible for final rule interpretation and dispute resolution. Has authority to forfeit a game in cases of unsportsmanlike conduct or repeated time violations.
- Deputy Chief Umpire: Assists the Chief Umpire and oversees assigned sheets.
- Game Umpires: Assigned to individual games to monitor play, verify scoring, operate measuring devices, and enforce rules.
- Eye on the Hog Operators: Monitor the electronic hog-line release detection system. In events without electronic handles, a human hog-line judge makes the call visually.
- Ice Technicians: Responsible for ice preparation, pebbling, nipping, and temperature control. While not match officials, their work is essential to fair play.
4.4 Coaches
Each team may have a designated coach who can communicate with players only during timeouts and between ends. Coaches are not permitted on the ice surface or in the field of play during live play. At WCF events, each team is allowed one 60-second timeout per game.
Section 5: Rules of Play
5.1 Game Structure
A standard game consists of 10 ends (8 ends in Mixed Doubles). Each end is analogous to an inning in baseball: both teams deliver all their stones, and then the end is scored. In the standard four-player game, each team delivers 8 stones per end (2 per player), for a total of 16 stones per end. Deliveries alternate between teams.
5.2 The Hammer (Last Stone Advantage)
The team that delivers the last stone in an end is said to have the hammer. This is a significant strategic advantage. At the start of the game, the hammer is determined by a draw-to-the-button (Last Stone Draw, or LSD) or coin toss. In subsequent ends, the team that did not score in the previous end receives the hammer. If an end is blanked (no score), the team that had the hammer retains it. Deliberate blanking — intentionally preventing a score — is a legitimate strategy to retain hammer for the next end.
5.3 Stone Delivery
The delivery is the fundamental action in curling:
- Starting position: The player places one foot in the hack and positions the stone on the ice ahead of the hack.
- Backswing and slide: The player draws the stone back, then pushes forward from the hack into a gliding lunge, sliding along the ice on the slider shoe.
- Release: The stone must be released from the hand before the near hog line. If the stone is not released in time, it is a hog line violation.
- Rotation (turn): As the stone is released, the player imparts a slow, deliberate rotation. An in-turn rotates the stone clockwise (for a right-hander), causing it to curl to the right. An out-turn rotates counter-clockwise, causing it to curl left. Typically 2–3 full rotations over the length of the sheet.
- Weight (speed): The force applied during delivery determines how far the stone travels. Weight control is one of the most difficult skills in curling and is measured by timing the stone between hog lines (split times).
5.4 Sweeping
Sweeping is a critical skill that allows players to influence a stone's speed and trajectory after release:
- Mechanics: Sweepers vigorously brush the ice surface directly in front of the moving stone. This friction heats the pebble, creating a thin film of water that reduces friction between the stone and ice.
- Effects: Sweeping causes the stone to travel farther (by reducing friction) and straighter (by reducing curl).
- Between hog lines: Up to two players from the delivering team may sweep their own team's stone from the tee line at the delivery end to the tee line at the playing end.
- Behind the tee line: Once a stone crosses the tee line at the playing end, only one player from each team may sweep it. The skip (or vice-skip acting as skip) of the non-delivering team may sweep an opponent's stone behind the tee line.
- No sweeping before hog line: A delivered stone must not be swept until it has crossed the hog line at the delivering end.
5.5 Free Guard Zone Rule
The Free Guard Zone (FGZ) rule is one of the most important strategic rules in modern curling. During the first 5 stones of each end (the first 5 delivered stones, regardless of team), any stone that comes to rest in the Free Guard Zone (between the hog line and the tee line, but not in the house) may not be removed from play by the opposing team. If such a stone is removed:
- The removed stone is restored to its original position.
- The offending stone is removed from play.
- Any other stones displaced by the violation are restored to their original positions.
Stones in the FGZ may be moved (bumped to a different position) but not removed entirely. Stones in the house are not protected by the FGZ rule. After the 5th stone of the end, all stones may be played freely.
5.6 Mixed Doubles Specific Rules
- Pre-placed stones: Before each end, one stone per team is pre-positioned — one as a guard in the centre line at the Free Guard Zone, and one in the back of the 8-foot ring on the centre line.
- Power Play: Each team may use a Power Play once per game (not in extra ends). When invoked, the pre-placed stones are shifted off the centre line to one side, creating an asymmetric setup. This is only available to the team with hammer.
- Sweeping: Either player may sweep any stone at any time, regardless of position on the sheet.
- FGZ: In Mixed Doubles, the FGZ rule applies to the first 3 delivered stones (not 5).
5.7 Strategy and Shot Types
- Draw: A stone delivered to come to rest at a specific location, typically in the house.
- Guard: A stone placed in front of the house to protect a scoring stone behind it.
- Takeout: A stone delivered with enough weight to remove an opponent's stone from play.
- Hit-and-roll: A takeout where the delivered stone rolls to a strategic position after contact.
- Freeze: A draw that comes to rest directly against an opponent's stone, making it difficult to remove without also removing the frozen stone.
- Raise: A stone that strikes a stationary stone (often a guard) and promotes it into the house or to a better position.
- Peel: A takeout of a guard where the delivered stone also exits play, clearing the path.
- Come-around: A draw that curls behind a guard stone and comes to rest in a protected position.
- Angle raise: A shot that strikes a stone at an angle to redirect it to a desired target.
5.8 Timing and Clocks
At WCF international events, thinking time clocks are used to manage the pace of play. Each team's clock runs only while that team is making decisions (from the moment the opponent's stone comes to rest until the delivering player's stone is released):
- 10-end games: 38 minutes of thinking time per team.
- 8-end games (Mixed Doubles): 22 minutes of thinking time per team.
- Extra ends: Each team receives 4 minutes 30 seconds of additional thinking time per extra end.
Travel time (walking between ends, getting into position) does not count against thinking time. If a team's thinking time expires, the team forfeits the game.
Section 6: Scoring
6.1 End Scoring
After all 16 stones (10 in Mixed Doubles) have been delivered in an end, the vice-skips from each team jointly determine the score. Only one team can score per end. The team with the stone closest to the tee (button) scores one point for each of its stones that is closer to the tee than the opponent's closest stone.
6.2 Determining Position
A stone must be touching or within the 12-foot ring (the outermost circle of the house) to be eligible for scoring. The ring lines themselves are part of the house. When it is unclear which stone is closest to the tee, officials use a measuring device that pivots from the tee to determine the distance from the centre of each stone to the tee. Measurements are taken from the tee outward.
6.3 Blank Ends
If no stones from either team are in the house at the conclusion of an end, the end is blanked (no score is recorded). The team that had the hammer retains it for the next end. Deliberate blanking is a common strategic tactic: a team with the hammer may intentionally remove all stones to preserve last-stone advantage for the following end.
6.4 Extra Ends
If the score is tied after the regulation number of ends (10 or 8), extra ends are played until one team leads at the conclusion of an end. Each team receives 4 minutes 30 seconds of additional thinking time per extra end. The hammer for the first extra end follows the standard rule (awarded to the team that did not score in the last regulation end).
6.5 Concession
A team may concede the game at any point by offering a handshake to the opposing skip. Concession typically occurs when the score deficit is too large to overcome in the remaining ends. Conceding is not considered unsportsmanlike and is in keeping with the Spirit of Curling.
Section 7: Violations & Penalties
7.1 Hog Line Violation
The delivering player must release the stone before it reaches the near (delivery-end) hog line. If the stone is not released in time, it is removed from play. At WCF events, the Eye on the Hog electronic handle system automatically detects the release point: a green light on the handle indicates a clean release, while a red light indicates a violation. In events without electronic handles, a hog-line judge makes the determination visually.
7.2 Touched Running Stone (Burned Stone)
If a moving stone is touched by a player, their equipment, or their clothing, it is considered a burned stone. The Spirit of Curling requires the offending team to immediately declare the infraction. The non-offending team's skip then has three options:
- Allow the stones to remain where they came to rest.
- Remove the touched stone from play and restore all displaced stones to their original positions.
- Place all affected stones where the skip reasonably estimates they would have come to rest had the infraction not occurred.
7.3 Free Guard Zone Violation
If a team removes an opponent's stone from the Free Guard Zone during the protected period (first 5 delivered stones per end, or first 3 in Mixed Doubles), the delivered stone is removed and the displaced FGZ stone is restored to its original position. All other affected stones are also restored.
7.4 Delivery Out of Order
If a player delivers a stone out of the designated rotation order and the error is noticed before the next stone is delivered, the stone is removed and redelivered by the correct player. If the error is not noticed until after the next delivery, play continues with the corrected rotation for the remainder of the end.
7.5 Stone Crossing the Back Line or Side Line
A stone that completely crosses the back line or touches the side line (or boards) is immediately removed from play. A stone that comes to rest between the hog lines without reaching the far hog line is also removed (unless it has contacted a stone already in play).
7.6 Time Violation
If a team's thinking time expires on the game clock, the team forfeits the game. This is strictly enforced at WCF international events. Teams are responsible for monitoring their remaining time.
7.7 Equipment and Conduct Violations
- Illegal broom heads: Use of non-approved broom head material results in disqualification from the event.
- Unsportsmanlike conduct: Deliberate interference, abusive language, or repeated refusal to comply with officials' instructions may result in forfeiture of the game or expulsion from the competition at the Chief Umpire's discretion.
- Electronic devices: Players may not use electronic communication devices or receive coaching signals during play (except during designated timeouts).
Section 8: Safety Considerations
8.1 Ice Surface Safety
- Footwear: All players and officials must wear clean, appropriate curling footwear. Slider guards must be worn when not delivering to prevent accidental falls.
- No running: Running on the ice surface is strictly prohibited. Players must walk carefully, especially when moving between ends.
- Awareness of moving stones: All personnel on the ice must remain aware of stones in motion. A moving 19 kg granite stone can cause serious injury to feet, ankles, and shins.
8.2 Equipment Safety
- Brooms: Brooms must not be thrown, slammed, or used in any manner that could damage the ice surface or endanger other players.
- Stones: Players must not drop or kick stones. Stones should be placed gently on the ice when being positioned.
- Stabiliser devices: Players using delivery sticks or stabiliser aids must ensure they are in good condition and do not leave debris on the ice.
8.3 Facility and Environmental Safety
- Ice maintenance: The ice surface must be properly maintained between games, including re-pebbling and temperature monitoring. Deteriorated ice with excessive frost, uneven pebble, or pooling water must be addressed before play resumes.
- Ventilation: Curling facilities must maintain adequate ventilation. Ice-making equipment that uses ammonia or other refrigerants must comply with local safety regulations.
- Emergency access: Clear pathways to exits must be maintained. First aid equipment and trained personnel should be available at all sanctioned events.
- Cold exposure: Players should dress in layers appropriate for extended periods in sub-zero temperatures. Facilities should monitor for signs of hypothermia or cold-related illness during extended competitions.
8.4 Warm-Up and Physical Preparation
Players should perform appropriate warm-up exercises before taking the ice, particularly for the lower body, core, and shoulders. The deep lunge required for stone delivery places significant strain on the hips, knees, and quadriceps. Stretching and mobility work helps prevent injury over the course of a multi-game event.
