An inside door panel is cut into a low inside panel (8) with a front frame unit (8a), a bottom frame unit (8b) and a rear frame unit (8c). Fitted with an internal side rail (4) a door support unit (6) designed as a plastic panel has hinge pegs (9) on the front edge and can be moved down and backwards into its final fitting position. The hinge recesses (10) have a diagonal line (10b) horizontally down and backwards. Pulley guides (11) on the plastic panel (6) operate window guides (13).
