I have built a table with keyed through slots and thought I would try this to define the corners before expanding the two sides for the keys . This little tool worked fantastic. I just installed it and hit it a few times and it exposed the top of the deep groove. This was great as it gave me a guide and a base to easily erase the rest of the groove with my chisels. This sped up my process and the slots were more accurate since I had multiple legs for this L shaped table I was building.