Third-file Rook

Name and setup

San means three. Counting from Black's left edge (9, 8, 7), the rook arrives on 7h; White's version puts it on 3b. A typical start is pawn to 7f, pawn to 6f and rook to 7h, followed by the same king walk as other Ranging Rooks: 4h, 3h, 2h, with the silver on 3h and a gold on 5h. The bishop moves to 7g when White's rook pawn reaches 8e, keeping 8f covered.

Why the 7th file

With the rook behind the 7f pawn, that pawn has backing for a later push to 7e. The push can lead to a pawn exchange on the 7th file, leaving the rook on an open line with a pawn in hand. It also places the rook on the side where the Static Rook player's attack usually arrives, so it meets that attack head-on.

The sharpest version pushes the pawn to 7e almost at once and is known as the Ishida style.