The Crescent Nicholson round knurl-cut chainsaw file with an American pattern. For ideal results, place file against beveled cutting surface of the teeth 20 to 45 Degree with saw and file from the inside to the outside of cutter. Sharpen all left-hand cutters on one side of the chain and move to the other side and file all the right-hand cutters. The height between cutting teeth and depth gauge is between.020" to.030" check the depth gauge height every 2 or 3 sharpening's. Tighten the tension on chain to firmly support cutters when filing.