The first rule here that does not look at one chord. Its condition is a pair: a dominant seventh, and after it a chord whose root sits a perfect fourth above — which is the ordinary way a dominant resolves. Its transformation then does something the other rules do not. It computes the replacement from the TARGET rather than from the chord being replaced.
Arriving from the other side
Take the chord being resolved to, drop a whole tone below its root, and build a dominant seventh there. That chord approaches the same arrival from underneath instead of from above. The two approaches share their sevenths and put their thirds a whole tone apart, so the target is unmistakably still the target — what changes is the direction the top voice moves to get there, and with it the whole colour of the arrival.
The name is the useful part: this is the back door into a chord that also has a front door, and a group can use either without anybody having to say which. It is heard most often approaching a tonic, where the front door is the dominant a fifth above and the back door is the seventh degree flattened.
Why the pairing matters mechanically
Because the condition reads two chords, this rule cannot be applied to a chord in isolation, and the engine has to look across bar lines to find its matches — which is exactly where real resolutions happen. The last chord of a section has nothing after it, so it never matches, and the tables below show that plainly rather than wrapping around to pretend otherwise.
Where it finds work
The blues offers it three pairs. Rhythm changes offers three in the A section and three more in the bridge, where every chord resolves up a fourth into the next one — which makes the bridge the clearest place to hear what this rule does, because you can compare eight bars of front door against eight bars of back door directly. The turnarounds offer it nothing: their roots move by fourths and fifths in a pattern that never puts a dominant immediately before a chord a fourth above it.