Abstract: A braking apparatus is described which is used to control the motion of a sliding platform of a pickup truck in order that the sliding platform may be stopped anywhere along its travel for convenience. The sliding platform is used to load and unload freight from the pickup truck when in an extended position at the rear of the truck. When the truck is parked on ground which is uneven the sliding platform is provided with energy which must be dissipated when it is moved from one position to another. When the usual braking device is released (usually a pin located appropriately in the tracks of the platform members) the sliding platform is in a “runaway” condition. The brake described here is capable of preventing this condition.