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