WA1844 TIRE MATING SQUARE IS USED TO CHECK DUAL TIRE MATING SO THAT TIRES ON DUALS ARE THE SAME DIAMETER. RIGHT AND LEFT DUAL TIRES SHOULD NOT VARY MORE THAN 1/2" IN DIAMETER. BY PLACING THE LONG ARM AGAINST THE SIDE WALL, THE SHORT ARM AGAINST THE TREAD, THE COMPARISON CAN BE MADE.