An integrally molded plastic part has a main body with an opening, and a door connected to the main body via an integral hinge and snapping into a closed position closing the opening. The door, at each of its two sides extending away from the hinge, includes a stopping surface via which the door, in its closed position, abuts against a supporting surface of the main body, and a snap-in hook protruding from the stopping surface and comprising a retaining surface which engages behind an edge of a flange confining the supporting surface. A distance between the two retaining surfaces as compared to a distance between the flanges confining the two supporting surfaces decreases with increasing distance to the hinge, whereas distances between the retaining and stopping surfaces as compared to distances between the edges of the flanges and the supporting surfaces increase with increasing distance to the hinge.