Lou,
You don't need a "CUT-OUT". You just need to mark the holes and your sill plate and drill for the existing mount bolts. The striker will be elevated by the thickness of the steel, but only a tiny bit. You can easily move the latch forward on your door to accommodate. You do need to bend the unit to match your door frame. I used my knees and formed the radius a little at a time to make a gradual bend. It just needs to be enough to allow you to push it into place, drill and screw. NOW MARK YOUR STRIKER HOLES FROM UNDER THE FRAME. Once you have some screws holding it down and in place, remove, drill, and install the interior. Then you can drill and install the remaining screws.
