Cross-pin

A pin exists when a piece cannot leave a line without exposing a more important target behind it. In a cross-pin, the same piece is subject to two or more pins at once, usually along crossing ranks, files, or diagonals.

A pin is absolute when moving the piece would expose its own king to check, making that move illegal. It is relative when moving is legal but would expose a queen, rook, or another valuable target. Because each side has only one king, at most one part of a cross-pin can be absolute; the others must be relative or depend on another serious consequence.

The tactical consequence

The restricted piece may appear defended or able to escape, yet leaving one line exposes the target on the other. It can therefore become a hanging piece, one the opponent can capture for material gain, or cease to perform a vital defensive duty. The motif often belongs to a longer sequence that adds attackers or removes defenders.

A defense must address both lines. An effective defensive move may capture or chase away a pinning piece, interpose another unit, move one of the targets behind the pinned piece, or create a more urgent threat. Solving only one pin may not release the piece.