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