I have just installed a Yale night-latch lock. There is a metal cover over the key-hole. This is loose, and often gets in the way of the key. I wanted to know whether it should be loose and what it is there for.
Are you referring to the thin disc of metal that spins around a bit in front of the keyway. It is designed to be of great annoyance to pickers/drillers and anyone with bad intentions in getting in without a key!!