Steve B wrote:

I need some pieces of flat bar a few inches long with slots going most of
their length. Thin stuff, actually about 1/16" thick, and steel.

What are they called, and where can I buy them in quantity?

Steve

Body shims. Autobody repair suppliers.

Used to align fenders and the like with the rest of the car.

Might do for what you want.

Cheers
Trevor Jones