{HEAD ~ The receiving portion} has {TAIL ~ a space} for pulling in the second end portion of the stopper 
has
{ HEAD ~ The receiving portion } has { TAIL ~ a space } for pulling in the second end portion of the stopper
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH