On the bottom of the discharge hopper are a series of discharge gates as shown in Figure 7‑32 that can be opened by operator control to discharge the aggregate. Each gate can also be opened or closed individually by a switch located at the top and in the front of the discharge hopper.

Check to see that they are correctly adjusted to close the gates fully. You will not be able to judge whether the adjustment is correct when the gates are open, until the spreader is actually dispensing aggregate.