A tire iron, also known as a lug wrench, is a tool used to loosen and tighten the lug nuts on a vehicle's wheels. It typically has a long handle for leverage and may feature a cross shape or a socket design to fit various sizes of lug nuts. Tire irons are essential for changing a flat tire or performing maintenance on a vehicle. Most vehicles come equipped with a tire iron in the trunk, often alongside a spare tire and a jack. Using a tire iron correctly ensures that the lug nuts are securely fastened, which is crucial for safe driving.