a) a door mounted on {TAIL ~ a frame} for lateral movement on tracks between {HEAD ~ a first open position} and a second closed position 
a ) a door mounted on { TAIL ~ a frame } for lateral movement on tracks between { HEAD ~ a first open position } and a second closed position
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH