Abstract: A lighting or indicating unit, such as a direction indicator, is fitted in a wing of a motor vehicle between the wing itself and a headlamp. A fastening means for fastening the unit includes a first zone of engagement between the unit and the adjacent wing, which defines a notional axis of rotation for the unit and determines, at least partly, the correct positioning of the latter with respect to the wing; a spring which applies a resilient force to the unit so as to apply a turning moment to the latter about the notional axis; and a second zone of engagement between the unit and the adjacent headlamp, this second zone being subjected to the turning moment and applying a reaction force which ensures that the unit bears on the wing in the first zone of engagement.