A height-adjustable support (10) for semi-trailers or similar, comprising a locally fixed external support tube (13), an internal support tube (14), which is fixed to a nut (18) on a spindle (17), the spindle being driven by a change-over gear and a bevel gear assembly. The change-over gear has two gear wheel stages which can be alternately activated, a separate gear stage comprising bevel gear toothing being provided for the distribution of forces after each gear wheel stage.