One-hand rule

The one-hand rule requires every move to be played with one hand. After the move is made, the player must press the clock with that same hand to stop their time and start the opponent’s. Moving with one hand while keeping the other ready over the button is not allowed.

The requirement covers every move, including moves with several physical actions. In a capture, one hand removes the enemy piece and places the capturing piece. In castling, the special move involving the king and rook, one hand moves both pieces. In promotion, when a pawn reaches the farthest rank and is replaced by a queen, rook, bishop, or knight, one hand removes the pawn and places the new piece. This includes turning it into a queen.

If a player uses two hands to make one move and then presses the clock, international rules treat and penalize the action as an illegal move, meaning a move that breaks the rules. Pressing the clock with the other hand also violates the clock-handling rule, but it should not automatically be confused with every case of physically making a move with two hands.

When a person cannot move the pieces or operate the clock, an assistant accepted by the arbiter, the official who applies the rules, may be authorized. That formal accommodation does not remove the rule for other players.