In this method, in {HEAD ~ the case} of trapping 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 
In this method , in { HEAD ~ the case } of trapping 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 HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH 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