Displacing {HEAD ~ a portion} of the YZ movement line allows {TAIL ~ vertical displacement} of the platform to be traversed 
Displacing { HEAD ~ a portion } of the YZ movement line allows { TAIL ~ vertical displacement } of the platform to be traversed
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH