positioning said cap on said cylinder, and aligning said third lock element with said fourth lock element, such that said third lock element mates with said fourth lock element to lock {HEAD ~ said cap} onto {TAIL ~ said cylinder} 
onto
positioning said cap on said cylinder , and aligning said third lock element with said fourth lock element , such that said third lock element mates with said fourth lock element to lock { HEAD ~ said cap } onto { TAIL ~ said cylinder }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL