Abstract: A brake wedge for rail-mounted cabinets which allows the movement of the cabinets to be automatically or manually prevented. The cabinet includes a number of wheels which are guided by floor-supported rails. The brake wedge has a curved profile and is operably connected to an actuating mechanism. The wedges are positioned adjacent each wheel of the cabinet and slightly above the rails. When the actuating mechanism is engaged by an object, one or more of the brake wedges are forced toward the wheels, causing the curved profile of the brake wedges to frictionally engage the wheels and thereby prevent further rotational movement of the wheel. A spring biases the actuating mechanism to an outward or normal position. The actuating mechanism, which defines an outer surface or portion of the base section, is preferably at or slightly above floor level and is thereby engaged and operated by virtually any object on the floor, such as a box or a person's foot.