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