chocking

Wheel chocks (or chocks) are wedges of sturdy material placed closely against a vehicle's wheels to prevent accidental movement. Chocks are placed as an added precaution in addition to setting the brakes. Their bottom surface is sometimes coated in rubber to improve grip with the ground. For ease of removal, a rope may be tied to the chock or a pair of them. One edge of the chock has a concave profile to contour to the wheel and increase the force necessary to overrun the chock. Most commonly, chocks are seen on aircraft and train cars.
Automobiles usually have parking brakes on the rear wheels. If the rear axle is jacked off the ground with only the parking brake set, the vehicle may roll on the front wheels and fall. Chocking the front wheels prevents this mishap. Motorcycle and bicycle chocks are bifurcated and fit around the wheel, supporting the bike and preventing its movement.
A wheel chock to hold automobiles and light trucks in place on rail cars was invented by Canadian engineer Robert B. Winsor (1939–2021).

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