Section 255(1) in The West Bengal Motor Vehicles Rules, 1989
(1)in order to prevent a goods vehicle from running backward on slopes, or otherwise to render it immobile. every such vehicle, not being a light motor vehicle, shall be equipped with two wedge-shaped rigid chocks, each measuring 30 centimeters in length, 30 centimeters in breadth and 254 millimeters in height, with one of its sides having a slope making an angle of 45 degree at the end. The plane surface of the sloped side of each chock shall be rendered concave so as to fit the outer circumference of the tyres normally fitted to the rear wheels of the vehicle.
