What White pieces are unprotected? Both rooks. What checks does Black have? Might as well be thorough about it: QxQ, Qxe3, Qf3, Qg4, and Qxg2. Do any of those also attack a loose rook? Yes, Qxg2; it wins the rook on h1 after White moves his king. This example illustrates the importance of habitually noticing checks on squares like g2 where enemy men currently sit.