In lithic reduction, pressure flaking is a method of trimming the edge of a stone tool by removing small lithic flakes by pressing on the stone with a sharp instrument rather than striking it with a percussor. This method, which often uses punches made from bone or antler tines (or, among modern hobbyists, copper punches or even nails) allows a greater method of fine control than even the most careful percussive flaking. Usually, the rough piece is held clasped in the flintknapper's hand, with a durable piece of fabric or leather protecting the flintknapper's palm from the sharpness of the flakes removed. The flintknapper places the tip of the flaking tool against the edge of the stone tool and presses hard, removing a small linear or lunate flake from the opposite side. In some instances, a hammer and punch is used while the tool is held down with a vice. The process also involves frequent preparation of the edge to form better platforms for pressing off the flakes, often using abraders made from a coarse-grained stone such as basalt or quartzite. Great care must be taken during this process, so that perverse fractures that break the entire tool do not occur. Occasionally, outrepasse breaks occur when the force propagates through across the tool in such a way that the entire opposite margin is removed, ruining the piece.