Elevate semi-trailers to loading docks for maximum serviceability during loading and unloading operations. Manufactured from heavy-duty aluminum tread plate for positive traction. All welded aluminum construction. 30,000 lbs. uniform capacity per pair (" thick material). Wheel Risers are designed to raise the trailer for loading and unloading to facilitate compliance with OSHA/ANSI B56.1 part 3 sec 7requirements for maximum grade of ascending or descending loaded fork trucks.