A 16mm T-spanner is a hand tool designed for screwing in and out spark plugs in vehicles. The tool features a T-shaped handle for better grip and leverage, allowing for both powerful and precise work, even in tight spaces. It is essential for engine maintenance tasks as it approaches spark plugs from various angles and corners, facilitating easier access. The 16mm size is specifically tailored to certain types of spark plugs, and its construction is typically robust and durable for long-term use in a variety of environments, from amateur garages to professional workshops.