This patented jig consists of a housing and two interchangeable seats, one closed and one open. The seats can swivel and be locked with the screw at any skew angle between 0 and 45 degrees. Skew chisels have symmetrical bevels on both sides. With this jig you mount the tool only once for grinding both the bevels. By turning the jig upside down you can grind both of the bevels symmetrically.