In the closed position, {HEAD ~ the doors} constitute {TAIL ~ side walls} to prevent removal of the freight from the vehicle 
In the closed position , { HEAD ~ the doors } constitute { TAIL ~ side walls } to prevent removal of the freight from the vehicle
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH