"Tried a cheaper Screwfix product but took it back and bought this one. Good decision! Why are there 2 catches enclosed? At first sight they look the same but look closer, one is for a square frame and one is if the window frames slopes a bit. How thoughtful! Handle was a bit stiff , needs a drop of oil.
I found it better to fix the handle first, go outside and fix window closed (with a bit of wood screwed to the sill). Back in side take your time to offer up the catch and hold it in place to mark screw holes. The first one you install will help figure best approach for next window (every millimeter counts!)"