A universally articulable supporting sheath comprises an interconnected series of links, each having a convex spherical surface at one end, and a concave spherical surface at its opposite end. The concave and convex surfaces mate with one another to form the sheath. Special links having branch openings may be provided. Various forms of waterproofing seals are provided, including O-rings, axially compressed rings, flexible belts, and ridges on the spherical surfaces. The links can be fitted together by thermal expansion. However, an axially split link is also described, which comprises two parts which snap together. The split parts may be molded as a unit with an integral thin wall hinge. The bending characteristics and bending radius of a sheath can be modified by insertion of spacers between the links at selected locations, or by the insertion of pins into radial holes provided in the links. Spacers with tongues may be used to prevent rotation of the links about the sheath axis, while allowing unidirectional articulation. Projections on one of a pair of mating spherical surfaces can be engaged with holes, slots or recesses of rectangular or other shapes to produce various limits on articulation and rotation. A single link may be provided with several alternatively usable holes, recesses and the like. The outer surface of a link can be provided with an axial extension engageable with a surface of an adjoining link to prevent back bending, or to prevent bending altogether.