Trailer (or semi-trailer)

Semi-trailers (also known as semi-trailers or simply trailers, and in English as semitrailers or just trailers) are trailers that transfer some of their weight onto the axles of a tractor unit with which they are connected via a fifth wheel coupling and kingpin. Semi-trailers are considered non-motorized commercial vehicles and must be driven on public roads with their own license plates.
In addition to their use in freight transportation, they are increasingly being used in agriculture. Semi-trailers with German registration typically have internal dimensions of 13.625 m × 2.48 m × 2.70 m and maximum external dimensions of 13.68 m × 2.55 m × 4.00 m. (Source: Wikipedia, Image: Andreas Hermsdorf / pixelio.de)