When hooked together, two pup trailers total about 56 feet, allowing companies to haul more freight than a typical semi-trailer. Read more: These Are The GMC Yukon Years You Might Want To Avoid ...

They're made up of two main parts: the semi-truck and the semi-trailer. Together, they form the full rig you see hauling goods across the country. Truckers sometimes drive the semi-truck without ...