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