Mirror fixings (Kennington OX1)

A couple of years ago we Freegled some Ikea "wavy" Krabb mirrors. Now I've discovered we still have the fixings. There are 4 fixed ones and 4 spring-loaded ones. I think the idea is that you screw them to the wall, then pull the spring-loaded ones to allow the mirror to be put in position before releasing. There are screws, but some of the heads are a bit worse for wear, so you might need replacements.