A curtain side trailer, also known as a curtain van or Tautliner, is a semi-trailer designed to combine the features of a flatbed and a dry van. It has a rigid frame, a headboard, a rigid rear door (or doors), and canvas curtains on the sides that can be retracted. This design allows for easy loading and unloading from the sides or rear while also protecting cargo from the elements when the curtains are in place.