Ever mindful of the enemy king, its constraints, and any of your pieces that attack it, you see that you almost have the makings of some sort of mate with the rook and bishop. Almost—but Black’s rook guards the back rank, his bishop guards f8, and his king has escape routes. Still, a mating threat that doesn’t quite work may still contain enough power to force a tactical gain by pushing Black’s king around. The standard inspection of any checks White can give turns up Rf7 and Rh1. Rf7 lets the king slip away to h6. Rh1 is different, though; with the dark diagonal forbidden to Black’s king by the bishop on c3, he has to move his king to g8—in line with his loose rook on d8. Now White is able to play his rook to h8, with the bishop on c3 furnishing cover. Black has to move his king off the back rank and allow White to play RxR, another little study in the back rank skewer.