Definition: The term "upleg" refers to a type of machine used in the production of heavy-duty vehicles. These machines are designed specifically for the construction and maintenance of large, semi-trailers or off-road trucks. Uplegs are typically powered by diesel engines and have high lifting capacities, allowing them to tow large loads with ease. They are commonly found on commercial trucks and are often equipped with advanced safety features, such as air bags and electronic stability control (ESC).