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.