Corridor mate

In a corridor mate, the king is confined to a line of squares like a corridor, while a rook, queen, or, in some classifications, a bishop gives check along that line. It is checkmate only when the king cannot escape, capture the attacker, block the line, or receive help from another piece.

The best-known case occurs on the first or eighth rank, the horizontal rows where the kings begin. The king's own pawns prevent it from moving forward, and a rook or queen attacks along the rank. That specific pattern is the back-rank mate.

The terminology is not fully standardized. Many sources use corridor mate as an exact synonym for back-rank mate. Others use it as a broader family covering horizontal, vertical, or diagonal corridors. In this glossary, corridor mate names the general confinement idea, while back-rank mate names the home-rank case.

Horizontal referenceVertical extensionDiagonal extension

The back rank as the reference

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The rook on h8 checks along the eighth rank; any horizontal escape would keep the king on the same line.

The king's own pawns seal the corridor

This is the back-rank case: the rook dominates the eighth rank, while Black's own pawns remove every exit toward the seventh.

1. The rook on h8 checks along the eighth rank; any horizontal escape would keep the king on the same line.
2. The pawns on b7, c7, and d7 form the wall that prevents the king from escaping forward.

The geometry matters more than the label: an open line carries the check, and the sideways exits are occupied or controlled. Typical defenses include creating an escape square in advance, guarding the line, capturing the attacker, or interposing a piece when the position allows it.