Repeat Pattern

 This motif has turned up in, I believe, three CT problems so far.

Its unusual enough for me to remember it clearly ( I think I took a long while finding the move when I first saw it ) and if that made me see it again for this problem it can only be a good thing.

As seems to happen a lot in chess,  the pin is a powerful weapon at any point in the game, but this has a good twist in the solution !

White to play after 1...Rf7