LEGO for grown-ups

Yesterday, I built a bookcase to help contain my growing DVD collection. It was my fifth (of various sizes and shapes) since I've been living in this flat and I think I'm getting better at constructing them. That said, there were still a few screws that didn't quite line up and needed to be forced in using my special technique of wrapping a rag around the handle of the screwdriver. For some reason, this makes things much easier (and less painful - although I still ended up with a blister). I'm sure there's a basic scientific principle in there somewhere...