The two flat head screws are a pain. The screws usually destroy themselves when removed. They aren’t cheap to replace at Numrich either. Think like 18 bucks each!
You can see the hollow tip of the screw protruding thru the rear sight housing. As you unscrew it, the cupped end tends to break. You can have a hell of a time reinstalling these screws if the threads are damaged bad enough during the break.