You drill through the paint and then you drill through plaster, which is that stuff smeared or covered on the wall during the decorating process. Once you've drilled your hole in the wall, you need a wall plug - there's actually several names for these,. They're called wall plugs, or roll plugs, I don't know if you can hear the difference; R-A-W-L roll plugs with an R. These are those plastic things that actually go into the hole, funny looking things, they've got spikes on them or whatever, and you push them into the hole to hold screws in place. The battery runs out quite quickly when you start pushing against the surface of