Clearance

Clearance means moving one of your own obstructing pieces so that another piece can use a square or operate along a line. The piece being moved is not an enemy target; it belongs to the same army, but it occupies the place or blocks the route needed for the sequence.

Two forms of clearance

• Square clearance: a specific point is emptied so another piece can occupy it, such as a queen needing a square from which the enemy king would have no legal defense.
• Line clearance: a vertical file, horizontal rank, or diagonal is opened for a rook, bishop, or queen. One move can accomplish both forms.

The clearing move must not give the opponent time to stop the continuation. It therefore often comes with a check, a direct attack on the king, a capture, or a threat that demands a reply. If the piece is deliberately given up to leave its square, the idea is a vacating sacrifice. If it moves away safely, the move is still clearance, but not a sacrifice.