Doors or gates are provided to control {TAIL ~ the amount} and width of {HEAD ~ the discharge} of particulate material to the highway surface 
Doors or gates are provided to control { TAIL ~ the amount } and width of { HEAD ~ the discharge } of particulate material to the highway surface
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH