The base of this jig is a torsion box made by gluing a top and bottom skin of 1/2" baltic birch plywood over a frame of 1" tall strips of 1/2" plywood. The base is 2" x 9" x 36", and the interior of the box has three rails which divide it into four 9" squares. Centered on the width of the base are two 6" x 24" plys of 1/2" b.b. which have been dadoed to accept a 24" long "T" track aluminum extrusion. This is screwed into place. Riding on top of this is a sled made of two 9" x 11" layers of plywood. These are held in position by two 1 1/2" x 11" rails glued under the sled edges. This sled needs to slide easily along the platform, but have no slop side to side. Drill both ends of the sled for a bolt which fits the aluminum extrusion so wing knobs can lock the sled in place.