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