The auxiliary blade is motivated to fold vertically pleatwise and, by alternating projection of the folded auxiliary forward of {HEAD ~ the trailing edge} of {TAIL ~ the main blade}, and a return to the overlying posture, respectively stop and reestablish the debris windrow 
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The auxiliary blade is motivated to fold vertically pleatwise and , by alternating projection of the folded auxiliary forward of { HEAD ~ the trailing edge } of { TAIL ~ the main blade } , and a return to the overlying posture , respectively stop and reestablish the debris windrow
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 HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH