On Thursday, 16 July 2020 21:01:10 UTC+1, Brian Gaff (Sofa) wrote:
"Smolley" wrote in message ...

Where could I get a piece of bent plywood, maybe 1/4" thick and 20" square
and bent 90 degrees.

You can't. There are many other ways to do it.

I want to make an 'armrest table' for my computer
chair. The idea is that the vertical side will slot down through the
cushions and the horizontal top to rest on the chair arm. This would
present a stable flat surface for the mouse and keyboard on the right hand
side of my swivel chair.

I've seen those usually made of some stuff called formwood, which I think is
a plastic that looks like it has a grain.
Brian

taste so bad it has form