Kill box mate

In the kill box mate, a rook stands next to the king and gives check. The queen protects that rook along the same diagonal, with one empty square between the queen and rook. Their geometry outlines an imaginary three-by-three box around the king.

The Box Is Sealed

8

7

6

5

4

3

2

a1

b

c

d

e

f

g

h

The rook attacks g8 and controls h7 from h8.

The rook checks and the queen supports

The rook gives check beside the king, and the queen completes the three-by-three box. f8 is controlled by the queen, and if the king tried to move there, leaving g8 would also open the rook's line.

1. The rook attacks g8 and controls h7 from h8.
2. The f6-g7-h8 diagonal protects the rook and closes g7.
3. The queen controls f7, another exit from the box.

The rook stops the king from moving away along its rank, a horizontal row, or its file, a vertical column. The queen covers diagonal exits and prevents the king from capturing the rook. The position is mate only when every remaining route is occupied or controlled.

The most useful recognition cue is distance: the king and rook are adjacent, and the queen is two diagonal steps from the rook. Before playing the move, verify that the queen truly protects the rook and that no defending piece can capture it or block the check.