{HEAD ~ A threaded mandrel} goes through the hole in the top of the cup shaped member and engages {TAIL ~ the expander member} of the rib plug 
engages
{ HEAD ~ A threaded mandrel } goes through the hole in the top of the cup shaped member and engages { TAIL ~ the expander member } of the rib plug
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH