A chock is a small block which is positioned underneath a wheel to prevent it from rolling. Chocks are used to secure vehicles of all shapes and sizes, and they are a common site at garages and other facilities where wheeled vehicles are routinely handled. The term “chock” may also be used to describe a support which holds a structure such as a barrel in place.
These blocks are designed in a wedge shape, with the thin point of the wedge facing the wheel, and the thick part facing outwards. The wedge is installed against the side which is most likely to roll, which can be based on the incline at which a vehicle is parked, the gear the vehicle is left in, or the vehicle's design.
Chocks are also known as “wedges,” in a reference to their shape. They can be made from plastic, wood, rubber, metal, and other materials, and they are often attached to a length of line so that they can be pulled away quickly. The rope or line also keeps the chocks firmly tethered so that they do not wander off, as garage equipment has an annoying habit of doing.
One of the classic uses of chocks is in the securing of aircraft. Once an aircraft has been parked, it will be chocked so that the craft cannot move. Planes can also be locked to chocks, as is done when a plane is repossessed by a lender, so that the plane cannot take off. Chocks for aircraft can be surprisingly small, as it doesn't take much of a wedge to prevent a plane from rolling.
Chocks can also be used to secure cars, although most cars have parking brake systems which are designed to prevent rolling. For extra security, mechanics can chock a car in place while they are working on it, or when they are working with a car which has a faulty parking brake. Big rig trucks, tractors, and other large vehicles may also be chocked for extra security, or to compensate for the lack of a parking brake, as are recreational vehicles.
Stores which supply parts and equipment for wheeled vehicles like planes, motorcycles, cars, and trucks usually carry chocks, in several different styles. If purchasers are not sure about which chock would be most appropriate for their use, they can ask staff members for recommendations. Staffers can select a size and design which is ideally suited to a particular vehicle, and they can provide information about the correct use of a chock.