A device, having a plastic molded part (1), in particular an add-on part and/or trim part for a motor vehicle, comprises a cover (2) for closing an opening (3) in a wall (4) of the plastic molded part (1). The cover (2) has a first rim (6) and a second rim (7), substantially opposite of the first rim (6), wherein the cover (2) has at least one retaining hook (9), which engages behind the opening (3) in the closed position of the cover (2), on the inner side (8) facing the opening (3) in the region of the first rim (6), and the cover (2) further has at least one detent element (10) on the inner side (8) in the region of the second rim (7), said detent element being latched in the closed position of the cover (2) to at least one detent counter element (11), fixedly attached to the wall (4). The cover (2) has at least one further additional detent element (12) on the inner side (8) in the region of the first rim (6), said element interacting with at least one additional detent counter element (13) at the wall (4), so that the cover (2) is held in the closed position at least substantially without prestress with respect to the opening (3).