{HEAD ~ a biasing member} adapted to apply {TAIL ~ force} to the stopper for pulling in the stopper into the receiving portion; and 
adapted to apply
{ HEAD ~ a biasing member } adapted to apply { TAIL ~ force } to the stopper for pulling in the stopper into the receiving portion ; and
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH