A lowboy is a semi-trailer with two drops in deck height: one right after the gooseneck and one right before the wheels. This allows the deck to be extremely low compared with other trailers. It offers the ability to carry legal loads up to 12 ft (3.66 m) tall, which other trailers cannot. Lowboys are used to haul heavy equipment such as bulldozers, industrial equipment etc.
The first lowboy trailer was invented in the 1920s; it featured a riveted gooseneck and solid rubber tires. The first detachable gooseneck trailer, referred to as an RGN (Removable goose neck), was invented in 1958.