What is the role of the handbrake when working on a car?

The handbrake, also known as the parking brake, plays a crucial role in vehicle safety, particularly when a car is stationary. Its primary function is to prevent the car from rolling when parked, ensuring that it stays securely in place, especially on inclines or declines. Engaging the handbrake locks the rear wheels, providing an additional layer of security beyond the regular foot brake. This is especially important to prevent accidents and ensure safety for the driver and others nearby.

While the other functions mentioned might relate to vehicle operation in some contexts, they do not pertain to the specific function of the handbrake. For instance, gauging power supply, serving as a visual indicator, or assisting with loading cargo are not relevant to the handbrake's purpose, which is solely focused on maintaining vehicle stability when parked.