In curling, players deliver a stone by pushing on the handle. They are required to let go of the handle before the stone crosses the near hog line. (There are two such lines on a sheet [the playing area], located 6.4 meters [21 feet] from each tee. Players must deliver a stone before it crosses the near hog line, and the stone must slide past the far hog line to remain in play.) Players are allowed to touch the handle as many times as needed before it reaches the hog line but may not touch it after the stone has crossed the hog line. An illegal second touch is called a double-touch violation and results in the stone being removed from play for that end. In elite competitions, sensors in the handle and the ice detect whether the handle was touched after the stone has crossed the hog line.
At the Milano Cortina 2026 Olympic Winter Games, a controversy erupted over alleged incidents of double-touching the stone. In a match between Sweden and Canada, the Swedish team accused a Canadian player of touching the granite after releasing the stone. Players are not allowed to touch the granite part of the stone at any point in play. Because the sensor is in the handle, it would not have detected a player illegally touching the granite part of the stone. In several subsequent matches, officials ruled that double-touch violations had occurred, including by Canadian and British curlers. Olympic organizers added referees to monitor the hog line at several matches but later reversed the unusual policy after outcry from players.