A gatebox for an aircraft comprises an opening operable to allow material to flow out of the gatebox, a hopper operable to direct material in the gatebox to the opening, a door coupled to the hopper and operable to move between an open position and a closed position by sliding along a surface of the gatebox, wherein the door comprises a front edge, a rear edge wider than the front edge, and at least two side edges that taper between the front edge and the rear edge, and a seal coupled to the hopper and operable to, when the door is in the closed position, engage the edges of the door and compress to prevent material in the gatebox from being released through the opening along the engaged edge of the door.
