It is just a style of threaded insert. There's two types: one particular is created to sort a bulge over the again aspect with the panel to be a screw is tightened in its threads. Another is similarly drawn in employing a screw, but is drawn in the sleeve alternatively https://jasperrjwkw.ampedpages.com/the-greatest-guide-to-threaded-inserts-for-plastics-54251506