providing {TAIL ~ a cap} having {HEAD ~ a third lock element} which mates with a fourth lock element on said cylinder; and 
providing { TAIL ~ a cap } having { HEAD ~ a third lock element } which mates with a fourth lock element on said cylinder ; and
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH