Abstract: The hinge element is comprised of two shells (10 and 11) made of dished metal plate which are assembled by means of a locking member comprising essentially a bolt (13) and a nut (15). Each of the two shells comprises a concave circular part having a flat bottom and an annular flange presenting undulated folds which are comprised of crests (19) and rounded hollows (20). The flange is generally interrupted at a mouthpiece (21, 24) to be fixed at one end of the longitudinal uprights of a folding support. Said hinge element is provided for assembling sections of a folding ladder or a scaffolding.