In the diagram, the clearance sacrifice 1.Rf8+ vacates the f7 square and, after 1...Rxf8 (better than 1...Bxf8 2.Qg8#), White utilizes the battery on the a2–g8 diagonal. After 2.Qg8+ Rxg8 (only move), White has a classic smothered mate with 3.Nf7#, utilizing the f7 square vacated by the clearance sacrifice.
