In the positions we just considered, the guard of the forking square always was under attack by one of your pieces, making possible an exchange that freed up the square for your knight. But what if none of your pieces are trained on the enemy pieces doing the guarding? Then capturing the guard won't work, but there are other questions we can ask. Here's a good one: is the guard also protecting some other piece or square that you might attack, thus distracting the guard away from its defense of the forking square? This theme—distracting the guard—is one we will consider at many points in these materials; it gets a chapter to itself toward the end.
In the example on the left, the arrangement of White’s e5 knight and the Black king and queen naturally suggest a fork with Nf7. The difficulty is that f7 is guarded by Black’s rook. This time you can't capture the rook, so ask if it protects anything else you can take. It does: White plays QxN; if Black recaptures RxQ, the f7 square is left loose and available for White’s knight. The fork Nf7+ then wins back the queen with the gain of a piece.