Pin (chess) Pin (chess) In chess, a pin is a situation brought on by an attacking piece in which a defending piece cannot move without exposing a more valuable defending piece on its other side to capture by the attacking piece. Moving the attacking piece to bring on the pin is called pinning; the defending piece so restricted is described as pinned. Only pieces that can move an indefinite number of squares in a horizontal, vertical, or diagonal line (i.e. bishops, rooks, and queens) can pin. Kings, knights, and pawns cannot pin. Any piece can be pinned except the king, since the
Chess piece makes the pieces bottom heavy and do not topple easily (a well-weighted piece should come upright even if bent to 60 degrees off vertical axis). This helps in blitz games as the speed of movement doesn't offer enough time or precision in dropping the pieces onto the intended squares. The length of each side of the squares on the chessboard should be about 1.25–1.3 times the diameter of the base of the king, or . Squares of about are normally well suited for pieces with the kings in the preferred size range. These criteria are from the United States Chess