A nerf bar is a tubular device fitted to the side of a racecar, typically single-seat race cars that compete on asphalt or dirt oval tracks. A "nerf" is a small, sometimes intentional, collision between two cars in which one driver bumps the other to facilitate a successful pass. The nerf bar protects the sides of the vehicles and also keeps their tires from becoming entangled. If fast-spinning tires come in contact with each other, one or both of the cars may lose control or even become airborne. Used on Asphalt

Asphalt

Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

 Modifieds such as used in the NASCAR Whelen Modified Series.

A more commercial application of the nerf bar is for convenience purposes on a pickup truck

Pickup truck

A pickup truck is a light motor vehicle with an open-top rear cargo area .-Definition:...

 or sport utility vehicle

Sport utility vehicle

A sport utility vehicle is a generic marketing term for a vehicle similar to a station wagon, but built on a light-truck chassis. It is usually equipped with four-wheel drive for on- or off-road ability, and with some pretension or ability to be used as an off-road vehicle. Not all four-wheel...

. It may act as a step to ease entry and exit from the vehicle, or to help prevent damage to the vehicle when crossing rocks off-road. Nerf bars can also be used to double as side bull bars on off-road vehicles.

The term is sometimes applied to the foot-rests on a motorcycle

Motorcycle

A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

. Nerf bars are typically made from either stainless steel, chrome or powder-coated steel, although there are considerable variations in style and design.

They are also variously known as step bars, boss bars, tube steps, step rails, truck steps, or step tubes.

Typically if they are being used to slide over rocks and past trees they are built with thicker tubing and attached directly to the trucks frame rails rather than the body. Being attached to the frame can allow them to support the entire weight of the vehicle and even be used as a jack point to change a tire. They are not called Nerf Bars any more and instead called Sliders, Rock Bars, or another variation of the two.