This is a part to replace a plastic part on a folding camp chair. The seat back upright rod passes through the hole at the rear of the seat, and the hole isn't necessary at the front, but that is the only difference I could see between the parts. I've got a couple of different brands of folding chairs, and it looks like this could be a fairly universal replacement.
I printed mine solid infill PETG and it is quite solid.
The chair originally had 4mm rivets holding everything together so 4mm bolts should work, or, as I found a #10 common nail fits nicely too. (there aren't any common imperial bolt sizes that are close enough to 4mm, 8-32 is too big, and 6-32 is too small)
Upper-Left-seat-support.stl | 533.7KB |