Adjustable supporting bracket having plural ball and socket joints

A supporting bracket comprising a first end element having a convex, spherical surface, a second end element having a concave, spherical surface, and a plurality of intermediate elements each intermediate element having first and second ends, with a convex, spherical surface at the first end and a concave, spherical surface, defined by a wall, at the second end, in which each convex spherical surface is in mating relationship with the concave spherical surface of another of said elements, in which each element has a passage, and having a cable extending through the passages, and means for tightening the cable and thereby causing the convex spherical surfaces to be brought into tight frictional engagement with their mating concave spherical surfaces, in which each convex, spherical surface has an outer diameter larger than the relaxed internal diameter of its mating concave spherical surface, and in which the wall defining each concave, spherical surface is sufficiently flexible to permit it to be brought into concentric relationship with the convex spherical surface with which it is in mating relationship, with the concentric mating surfaces in area contact with each other.