said door being slidably mounted on {TAIL ~ said box} for selective opening and closing of {HEAD ~ a discharge slot} along the width of said hopper bottom 
said door being slidably mounted on { TAIL ~ said box } for selective opening and closing of { HEAD ~ a discharge slot } along the width of said hopper bottom
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 OTH OTH OTH OTH OTH OTH OTH