Here's a different application of our current logic. White already seems to have the makings of a pin of Black’s bishop, but it’s not quite there because the piece behind the bishop—Black’s d8 rook—is protected by Black’s other rook on a8. Thus Black's bishop can move without worry. How can White improve on this? It would be nice if he could loosen the Black rook on d8, but he can’t. What he can do, however, is play his own rook on h4 to d4. This has the same consequence as loosening the rook on d8, because now that rook has two pieces aimed at it and still is protected just once. This means the bishop no longer can move freely; White takes it next move with RxB. Here we see an alternative to loosening a piece in order to create a pin in front of it; instead you can amass enough force to make the piece in the rear overmatched if the piece in front of it moves.