The laser-cut plywood clamps holding the timing belts to the drive ribs slant diagonally across the rib + belt and secure one edge of the belt.
While this certainly works, it offended my sensibilities and is probably why the instructions call for that low-profile bolt.
Introducing the belt clamp to Mr Disk Sander provided just enough relief to clear the belt’s backing, while not making for a sloppy fit. In round numbers, if you barely trim off the plywood veneer it’ll be about right. Use an ordinary file if one of Mr Sander’s relatives doesn’t live in your shop.
And then it works just like it should. If you were even fussier, you might chamfer the outer edges to allow the belt to lie flatter against the rib, but that’s in the nature of fine tuning. At least on my Thing-O-Matic, there’s plenty of air between a standard bolt head and the adjoining carrier rod.
This is obviously not something you should dismantle your Thing-O-Matic for, but if you’re in the delightful position of facing that mountain of parts, this is perfect timing.