The invention relates to an arrangement of fastening means for an element such as a roof bar on a double-wall structure such as the roof panel of a motor vehicle, the fastening means comprising, for each fastening point (13) of the element on the structure, a fastening barrel (17) integral with the element and passing through a first (21) of the two walls (21, 22) of the structure (2) by a first orifice (23) to bear on the second (22) of the two walls (21, 22), and a screw/nut assembly (4) whose screw (41) is housed inside the fastening barrel (17) and projects from the two opposite ends of the fastening barrel (17) so as to pass through the second wall (22) of the structure by a second orifice (24), the fastening barrel (17) presenting a clearance between the screw (41) of the screw/nut assembly (4) and an inner face of the fastening barrel (17) and an outer diameter of the fastening barrel (17) being substantially equal to the diameter of the first orifice (23), so that the fastening barrel (17) passes through the first orifice (23) substantially without clearance.
