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