On the surface this position does not look much like the others in this chapter, but again a scan of the king’s file turns up two enemy men in line with it—a piece (the queen on g2) and a pawn (on g7). If the pawn were out of the way, White could pin the queen with Rg1. Threatening the pawn won’t work; you can’t scare a pawn if it has protection, and even a frightened pawn can’t move off of its file. The standard way to clear an enemy pawn, rather, is to take something it protects, inviting the pawn to move off its file to perform the recapture. The g7 pawn protects the knight on h6, so White plays RxN; Black replies g7xR; and now Rg1 pins Black’s queen, with protection furnished by the knight on e2.
You might think you could also make gains here by playing the same idea in reversed order: Rg1; then, when the Black queen moves, Rh5xN, with the pawn on g7 pinned and unable to recapture. Not quite, however. Black replies to Rg1 with Qxf2; and then if White takes the h6 knight with his other rook, Black has Qxe3—a fork of White’s h6 rook and his bishop on d3, both of which are loose. White still can pull his chestnuts out of the fire by moving his queen to d6 (threatening Black’s loose bishop) and then to h2 (threatening to mate with the rook already on the h-file), but these kinds of complications are beyond the scope of the current lesson.
Still, it's worth studying the initial forking idea for Black here that makes Rg1 not so attractive as a first move for White. It would be easy to overlook; a key to not overlooking it is to be mindful at all times of loose pieces on the board—your own as well as your opponent’s. As White you should realize that you have a loose bishop already on d3 and that your rook currently on h5 will be left loose on h6 after the capture. Loose pieces are a big deal. They make good targets for forks, especially by your opponent’s queen. Since the whole idea of starting with Rg1 would be to drive off the Black queen, you have to ask whether the queen, once driven off, could go make trouble for the loose material you would be leaving around the board. It could indeed.