In this method, in the case of trapping {HEAD ~ the movement} of {TAIL ~ the rear pane} in the lowering direction is stopped and the rear pane is reversed, i.e. moved in the lifting direction 
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In this method , in the case of trapping { HEAD ~ the movement } of { TAIL ~ the rear pane } in the lowering direction is stopped and the rear pane is reversed , i.e. moved in the lifting direction
OTH OTH OTH OTH OTH OTH OTH OTH OTH 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 OTH OTH OTH