In doubles curling each two-person team plays with six stones, one of which is positioned in play before the start of the
end. One stone is placed on the center line in the
4-foot circle of the
house such that the back edge of the stone is aligned with the back edge of the circle. The other positioned stone is placed on the
center line as a
guard in front of the house. The exact placement of this positioned guard is chosen from six possible locations and must be agreed upon by the teams before the game. The six possible locations are immediately in front of and behind three points along the center line: the midpoint between the
hog line and the front of the house, and 3 feet in front of and behind that midpoint. The teams decide on the guard location based on ice conditions, such as the amount of
curl expected, and the same location must be used the entire game. The team that did not score in the previous end decides which team's stone is placed in the house and which team's stone is placed as a guard. The team whose positioned stone is the guard throws the first stone that end. In high-level play, teams therefore usually elect to have their stone placed in the house, to keep the advantage of the
hammer. If there was no score in the previous end then the team that threw the first stone gets to decide which team's stone goes where; this means that unlike in traditional team curling, the team with the hammer does not usually get to keep it if the end is
blanked. The team that has the decision on the placement of the positioned stones also has the option to use their power play. Each team may use the power play only once per game and it cannot be during an
extra end. The power play allows the positioned stones to be moved to the side of the sheet (which side is at the discretion of the team using the power play) with the back edge of the stone in the house positioned on the
tee line where the
8-foot and
12-foot circles meet and the guard correspondingly moved to the side of the guard zone. Of the five stones each team delivers during an end, one player throws the first and last stone while the other player must throw the three in between. Unlike in traditional curling, the throwing order may change between ends. In high-level mixed doubles play, it is common for the female partner to deliver the first and last stones, and for the male partner to deliver the middle three. The player that is not delivering the stone may act as a sweeper or as
skip at the far end, and the player throwing the stone often gets up after releasing the stone to sweep. No stone, including those in the house, can be removed from play prior to the delivery of the fourth stone of an end. If there is a violation, the delivered stone is removed from play and any stones moved are returned to their original position by the non-offending team. The game is scored the same as traditional curling, where the team with a stone in the house closest to the
button scores one point for every stone in the house closer to the button than the closest opposing stone. A game is completed after eight ends unless an extra end is required due to a tie, or if a team concedes before reaching that point. == Rule changes ==