Abstract: Apparatus for loading bulk materials from a storage bin into a truck body. An enclosure is defined by flexible rubber movable walls of which at least three are horizontally displaceable into contact with the corresponding sides or edges of the body of the truck to be loaded. Exhaust fans cause a negative pressure inside the enclosure sufficient to urge the movable walls into sealing contact at the corners of the enclosure and against the sides or edges of the truck body. At the end of loading, detectors automatically cause the horizontally displaceable walls to move back out of contact with the truck body to facilitate ingress and egress of the truck.