Abstract: A door construction utilized to control the discharge of material, especially particulate material such as feed and grain, from the outlet of a receiver in which the material is being processed or stored. The structure employs a door member in the outlet which slides in a self-cleaning, inclined track formed by a pair of rails at each side margin of the member. The outer rail of each pair is in surface contact with the respective margin, whereas the inner rail is essentially in line contact with the margin and is part of a transversely U-shaped component that provides a passage along the margin which receives material that may enter the track. Such material is conveyed by gravity flow through the track passages and returned to the receiver, thereby providing the self-cleaning action to prevent the door member from freezing in the track and also preventing leakage of material when the door member is shut.