When the fifth wheel coupler is connected to the pulley system, {HEAD ~ the coupler} can be moved into and out of {TAIL ~ engagement} with the king pin 
When the fifth wheel coupler is connected to the pulley system , { HEAD ~ the coupler } can be moved into and out of { TAIL ~ engagement } with the king pin
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH