It's really a sort of threaded insert. There's two kinds: just one is made to kind a bulge on the back side on the panel to be a screw is tightened in its threads. The other is likewise drawn in utilizing a screw, but is drawn in the sleeve instead https://car-filters30739.ampedpages.com/the-smart-trick-of-fasteners-for-wood-that-no-one-is-discussing-54286631