I'm still trying to put together a basic flint knapping kit, so I went over to lowes to get a grinding wheel. While I was there I decided to look and see if I could find something to use as a hand pad for pressure flaking. They had just the thing over near the concrete section. In the knee pad section they had solid rubber knee pads for about 9 dollars a pair. It looks like you can get 3 or 4 out of each one. The question I have is about how I should cut the groove and also what is the purpose of the groove? I would be thankful for any helpful info.