{TAIL ~ a first rotatable means} for controlling the horizontal movement of said cover through {HEAD ~ Said linear means}, 
{ TAIL ~ a first rotatable means } for controlling the horizontal movement of said cover through { HEAD ~ Said linear means } ,
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH