{TAIL ~ a recessed portion} therein communicating with said {HEAD ~ second opening} and adapted to receive said keeper element therewithin, 
{ TAIL ~ a recessed portion } therein communicating with said { HEAD ~ second opening } and adapted to receive said keeper element therewithin ,
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH