I'm thinking maybee pins that slide in short sections of pipe?

FWIW, 5/8" bolts are usually an OK fit in 1/2" black pipe,
you may or may not have to drill them out to remove the
welding ridge inside. I've also use 5/8 OD x 1/2" ID
oilite flange bushings in same.

HTH,
--Glenn Lyford