Abstract: A coupling for a fiber optic cable includes a sleeve of non-light transmissive material having external threads on each end and an axially central radial projection. The core extending through the sleeve has opposed frusto-conical surfaces. An adapter is threaded on the core and shaped to conform to the termination element of the cable to which the coupling is to be connected.

Abstract: A first structural member having a portion beveled at an angle of 45.degree. which includes a mortise in the form of a generally cylindrical groove is joined to a second structural member having a portion beveled at an angle of 45.degree. which includes a tenon in the form of a generally cylindrical rib, with the beveled portions in an abutting relationship by a joint formed by the rib being snugly fitted in the groove. The members may be joined at a straight angle or at a right angle, and may be employed for producing modular structural frames; articles of furniture; modular toy constructions; wall attachments; flooring boards and other arrangements wherein the flexibility of straight angle and right angle permutations of interlocking members of standardized elongated configurations are utilized.