The jig was used to scribe the inside cut of the flange onto a piece of 1/4-inch-thick 6061-T6 aluminum. The outside cut line was scribed 1/2-inch outside of the inside line, and the flange was cut. Note the inside access cut at the lower left (arrow). Once the interior and exterior cuts were complete, the access cut was welded up and sanded smooth. Since the flange is under some stress when bolted to the head, 4043 aluminum rod was used on this weld.