Abstract: A modular support (7) with holes (10) for attachment screws is equipped with a through seat (7A) with axial stop (7B) for a nut (9) capable of being received and engaged in said through seat; the modular support (7) can be utilized simply by preparing—on the load bearing structure—the threaded holes for the screws and a trace for a transverse spline, partly received in another trace (16) in the support (7).