A steering wheel is an example of a wheel and axle, which is a simple machine. A wheel and axle is a large wheel attached to a smaller wheel, called the axle. When the smaller wheel is turned, it causes the larger wheel(s) to also turn. The smaller cylinder-shaped wheel connects the wheels on a car. When the axle is turned, the wheels turn together, allowing the car to move forward or backward. Other examples of wheel and axle include doorknobs, windmills, and bicycle wheels.