Abstract: The spreader comprises an elongated hopper which is mountable across the rear end of a truck box in an underslung fashion. When the end-gate of the box is opened, aggregate can spill into the hopper. The hopper forms a discharge slot along its lower end. A pair of coaxial, end-to-end drums are rotatably mounted in the hopper and extend into the lower portion of the slot. Each drum is separately driven. A ramp extends between the box floor and the front upper quadrants of the drums for feeding aggregate thereto. A pair of separately actuated, pivoting flaps bear against the upper rear quadrants of the drums and function to open or close the upper portion of the slot. The ramp/drum assembly provides even, well distributed discharge of aggregate. The flap/drum assemblies can provide an effective shut-off or lay down narrow or wide strips of aggregate.