Abstract: A hopper discharge structure is provided with slope sheets defining a throat over a pneumatic outlet tube. The throat is closed by two sliding valve plates. The valve plates are moved by crank arrangements which provide an operator with varying mechanical advantage in operating the valve means. The crank arrangements are mounted on operating shafts extending the length of the hopper. The operating shafts extend through the hopper end walls and are adjustably supported for rotation by reinforcement plates adjustably mounted on the end walls. The operating shafts are equipped with handles which accommodate the insertion of an extension bar from two different directions. The outlet tube is covered by a hinged cap and locking structure. The cap is cammingly sealed over the end of the outlet tube by a cam lock and handle mounted on the locking structure. Outward force on the handle unlocks and withdraws the cap from the end of the outlet tube.