A cylindrical item which may have wrenching and/or driving facilities and/or shoulders. It is designed to be inserted in a drilled or a pretapped hole, or molded or pressed into soft material to reduce the size of a tapped hole; to provide threads; to add strength, and/or to prevent stripping. It is one of the following: (1) a one-piece, flanged or unflanged, internally threaded item which may have external threads, and/or serrations around the periphery of the collar, designed to engage a serrated lock ring which is not included with the item; (2) a one-piece precision coiled wire; (3) a two-piece item consisting of an internally threaded cylinder and a mating externally threaded part; or (4) a one-piece internally threaded item whose outside diameter is tapered and/or knurled and/or with fi (s) . The internal thread of the item may have a locking feature. Excludes items having a sleeve on its underportion which can be clinched or crimped. Excludes bushing, machine thread; nut, plain, knurled; nut, plain, round; nut, plain, clinch and nut, self-locking, clinch. See also nut, plain, plate.