Just a piece of track in a piece of 3/4” ply.
The insert is held to the saw plate with bolts and wing nuts.
In use, just line up the blade side of the jig with your cut lines and clamp. Always clamp on the good side so the blade cuts in the “waste”.
Two critical requirements:
1. Insure that the ply is wide enough so that, when the saw is in use, there is enough room for it to pass the clamps. Also, make it wide enough so that the initial cut will establish the cut line.
2. If you must drill holes in the plate for the attachment bolts, insure that both they are both the EXACT same distance from the blade. I was lucky. The old Skill 77 had stock holes.
You’ll note that I mounted the insert with a bit sticking out the front of the saw plate. Makes it easier to see when inserting it into the track.
-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton