SPECIALLY DESIGNED CHOCK FEATURES ""TOOTH"" LIKE BOTTOM CLEATS THAT GRIP ICY OR SLIPPERY SURFACES FOR MAXIMUM HOLDING POWER. HEAVY DUTY FORMED STEEL CONSTRUCTION IS POWDER COATED IN HIGH VISIBILITY SAFETY YELLOW FOR MAXIMUM CORROSION PROTECTION. COMPLY WITH OSHA REQUIREMENT 1910.178(K)(1) TO PREVENT MOVEMENT OF TRUCKS OR TRAILERS WHILE LOADING OR UNLOADING. RECOMMENDED TO BE USED IN PAIRS.