Abstract: A box-like sealable container for transporting and discharging material includes an improved tailgate and tailgate seal. The container has walls which define an opening, and the tailgate attached thereto has a periphery that overlies the opening. The tailgate seal is an elongated tubular member mounted inside a metal channel fastened on an outer wall of the container about the opening. When pressurized, the tubular member expands out of the channel and sealingly engages the tailgate if the tailgate is in a closed first position. Reinforcement members mounted on an outer wall of the tailgate prevent tailgate distortion.