Transport container device for vehicles, e.g. device with loading opening

The ski carrying system (10) incorporates a seat (13) with a backrest (11) and a headrest (12). There is a rectangular aperture (D) in the backrest. A removable rectangular cushion (E) may fill this aperture. It may have flat rear and front surfaces (22,23). There are matching fastenings (32,34) at the sides of the cushion and the aperture and at the top (27,28).