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