Rooks behind passed pawns

Tarrasch's rule, on the board.

The most useful rule in rook endings: put your rook BEHIND a passed pawn. Behind your own passer, the rook supports its march and gains scope with every step the pawn takes. Behind the enemy's passer, it ties the defender down. A rook stuck in FRONT of a pawn is passive — it has to move out of the way the moment the pawn advances.

In the diagram, White's rook sits behind its own a-pawn, ready to escort it home, while Black's rook is reduced to a passive blockade in front on a8. Two rook-and-pawn positions are worth knowing cold: the stronger side wins with the Lucena — 'building a bridge' with the rook to shield the king from checks — and the weaker side holds the Philidor draw by keeping the rook on its third rank until the pawn advances, then checking from behind.

White's rook is behind its passed a-pawn (active); Black's rook is stuck in front on a8 (passive).

Where does a rook belong relative to a passed pawn?

Answer the question to keep going!