The invention provides a receiver structure for receiving a light unit having a glass for fitting to a motor vehicle fender, the fender and the glass including means for putting the glass of the light unit into a reference position relative to the fender, the receiver structure comprising: fastener means for fastening the receiver structure to the fender; and fastener means for fastening the light unit to the receiver structure, which means conserve the reference position of the glass relative to the fender as imposed by the means for putting the glass into a reference position. The invention also provides an outside module for a motor vehicle, a fender, and a method of mounting a light unit on a fender.