I first tried to build keystones by holding them in my palm, it creates quite a balancing act holding them as you coordinate the wires into the correct slot while using the punch down tool. Not too mention the possibility of punching down on your palm and cutting yourself. This tool helped a great deal by holding the keystones in their place, protecting my palm and increasing my productivity tremendously. It comes with three compartments (A,B,C) which confused me at first, since there was no insSee full review