Abstract: The invention relates to a fastener device for fastening to a support plate, the device being constituted by a rider having a first fork whose two branches define an internal outline designed to co-operate with a polygonal element of a junction member to be held so as to prevent said junction member from rotating, and on the other side a second fork whose two branches can be placed astride an extension portion of the junction member, which branches are bent so as to bear both against the other face of the support plate and against a terminal shoulder of the extension portion so as to urge the junction member against the stop face of the plate, thereby holding said junction member against translation.