oh yeah, I knew a guy who had a large chisel, and a sledgehammer? (looks like a sledge, small enough to be used with one hand) and he could not focus on both the end of the chisel and the other end where he would hit with the hammer. He tried and tried, and finally gave up and only focused where he placed the chisel, and put the end of the thumb on the end of the chisel, and gave it a good go with the sledgehammer. I don't know if his thumb ever got 100% right again. Be careful with the tools. :D