the arrangement of the plurality of second rotatable means and endless linear means being such that the operation of the first rotatable means causes the simultaneous movement of the opposed side portions of the cover to retractably move {HEAD ~ the cover} over {TAIL ~ the top} of the trailer body 
the arrangement of the plurality of second rotatable means and endless linear means being such that the operation of the first rotatable means causes the simultaneous movement of the opposed side portions of the cover to retractably move { HEAD ~ the cover } over { TAIL ~ the top } of the trailer body
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 OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH