said {TAIL ~ first and second openings} having cross sectional configurations of a type to allow passage of {HEAD ~ said keeper element therethrough}, 
said { TAIL ~ first and second openings } having cross sectional configurations of a type to allow passage of { HEAD ~ said keeper element therethrough } ,
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH