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