Mate with the rook

Step 1

A rook and king mate on the edge of the board: the two kings face each other, and the rook checks along the edge.

Step 2

The rook checks on the eighth rank; the white king covers every escape.

The moves: 1. Rh8#

Step 3

White to play: mate in one.

White to move.

Step 4

Black to play: mate in one.

Black to move.

Step 5

Where does the rook-and-king mate always happen?

1. On the edge of the board
2. In the centre
3. Anywhere at all