Which safety precaution should be taken before working under a vehicle?

The correct approach before working under a vehicle is to ensure that the vehicle is securely supported on jack stands. This is crucial for safety, as vehicles can be heavy and if they are not properly supported, there is a risk of the vehicle rolling or falling while a technician is working underneath it. Jack stands provide a stable support system that greatly reduces the risk of serious injury.

Keeping the engine running could introduce unnecessary hazards, such as exhaust fumes or unexpected vehicle movement if the brakes are not engaged properly. Using only one jack poses a safety risk, as it may not securely hold the vehicle in place, leading to a potential collapse. Lastly, working without gloves can expose a technician to sharp edges or other harmful materials, which can lead to injury. Thus, the priority should always be proper vehicle support before any underneath work begins.