Triangle mate

In a triangle mate, the queen gives the final check and a rook protects it from the same file, the same vertical line of the board, with one empty square between them. The queen, rook, and king create a visible triangular shape.

A rook-supported vertex

8

7

6

5

4

3

2

a1

b

c

d

e

f

g

h

The queen on g6 checks the king on h7.

The g-file completes the triangle

The queen mates from one vertex of the shape. The rook protects it on the g-file through the empty g5 square, and a black piece blocks the remaining retreat.

1. The queen on g6 checks the king on h7.
2. The rook on g4 protects the queen on g6 through the empty g5 square.
3. The black bishop on h8 occupies the only retreat outside the queen’s control.

The queen normally stands close to the king and controls several exits. The rook makes it impossible for the king to capture the queen and adds vertical control. The board edge or a defending piece blocks the remaining route.

The geometry is a memory aid, not proof of mate. Verify that the line between rook and queen is clear, that the rook truly protects the queen, and that every king square is attacked or occupied. It resembles kill box mate, but there the rook gives check and the queen supplies the support.