right on. thats what i was looking for.
that mushroom is for a blind, NON threaded hole.
anyway, you unscrew it aways, push it into a hole(not threaed) and just start to tighten it up. the 2 angled parts pull against each other causing it to get tighter.
its got a knurled head tho, seemingly for hand tightening. where it that supposed to go?