The support bar has an adjustable holder with a spacer for the crosspiece (2). A threaded-pin with a collar (12) is adjustable in one threaded-sleeve (10) sitting on a lug (8). The threaded-pin passes through a slot (6) in the crosspiece which in turn leans on the collar. The crosspiece is clamped between the collar and nut. The slot is transverse to the longitudinal direction of the crosspiece. The pin has a groove in its head. The lug has at least one slot running transversely to its longitudinal direction. Ribs are arranged inside the flange. There are a row of apertures (5) provided in each rib for mounting metal fitting.
