Motor vehicle body side wing in plastic material provided with an indexing device

The fender has an indexing device with a plastic indexing part (11) that is supported by a rib (4) and projected from an internal side of the fender. The part (11) cooperates with a part of a case (6) and an indexing finger (15) to position the fender with respect to a headlight (2). The part (11) and the rib are placed, such that an end of the fender is positioned at a preset distance with respect to the headlight.