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