Abstract: A discharge control apparatus for the rear slide gate on the tail gate of a truck box comprises a rod mounted horizontally across the tailgate from a free beyond one side of the tail gate. The rod is formed in two portions which can divided as a coupler between a center section of the tail gate and a side section of the tailgate. The rod portion of the center section is connected by a pair of cranks to the slide gate. A lever on the free end of the rod can be rotated manually and the rod locked at a required position to hold the slide gate at the required opening. The coupling can be disconnected by pulling the side rod portion away from the center rod portion to allow the center section to be opened.