A mechanism for controlling opening of doors on a hopper car underside. The mechanism includes a pair of stationary hook assemblies located outboard of a discharge opening and having a proximal end affixed to the hopper car and a distal free end. Each hook assembly includes a locking cavity bounded by a cam locking surface and a distal slide surface. Included also is a pair of locking cam assemblies having an upper and lower cam surface matable with the hook cam locking assembly and having a slot. An elongate member has ends affixed to the pair of locking cam assemblies and extends through each of the annular end bearings. A pair of annular end bearings is disposed adjacent to the locking cam assemblies and each affixed to a door.