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