Abstract: The trailer comprises a rectangular framework, a loading box fixedly mounted on the framework and including a horizontal platform, and a group of freely rotatable carrying wheels which allow the trailer to be pulled. The trailer is characterized in that two frames are disposed underneath the framework and are arranged to engage one frame into the other one between an expanded position of the trailer where the frames are drawn apart from one another and a retracted position where the frames are drawn in towards one another. The framework holds the frames with supports, that are arranged to permit a simultaneous transverse and longitudinal movement of the frames with respect to the framework when said frames are moved between an expanded position and a retracted position.