It's a sort of threaded insert. There's two kinds: just one is made to kind a bulge over the back side on the panel to be a screw is tightened in its threads. The opposite is in the same way drawn in using a screw, but is drawn in to https://beretta92fsaluminumgrips87525.full-design.com/the-best-side-of-threaded-inserts-for-plastics-69628258