This is a style of threaded insert. There are two forms: one is intended to variety a bulge over the back aspect with the panel to be a screw is tightened in its threads. The other is similarly drawn in using a screw, but is drawn in the sleeve instead https://magazineextension32086.pointblog.net/new-step-by-step-map-for-threaded-inserts-for-plastics-67577290