Cutting board glue up jig

Weld up a frame out of angle iron, preferably bed rail, it’s hardened, 4 sides to fit the wood being used. lay in enough glued strips to fill most of the frame. Drop in a cull on the side where you drilled and tapped several holes, insert bolts and tighten against the wood cull untill it’s dry. There’s your basic idea. Bed rails are usually FREE, bolts are reasonabally priced. Oh, you should use Allen Head Cap Screws because they are usually hadened too. If you need a picture I’ll draw you one.
MIKE

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Quoin Keys

And a Quoin

A QUOIN for printing would work even better if you can get them. Quoin – Printing . a wedge of wood or metal for securing type in a chase.

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pipe clamps? Cheap easy to use and not complex.

You didn’t say what the disability was beyond developmentally. Makes all the difference in the world what you ask ‘em to do.
Are they given to sudden rages which are expressed in physicality? If so maybe pipe clamps wouldn’t be the best.

You also didn’t specify how many boards would be under assembly at any one time

If it’s a small number a few jigs made from a couple layers of 3/4 ply might be sufficient use long taper wedges to do the clamping paint ‘em with spray enamel and wax the paint to keep glue from stickeing

Make the channel in the ply for the all-thread by grooving the ply before assembly.

You could make it more complicated, but I rather suspect that tapered wedges will do the job well enough

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