Abstract: A fastener consisting essentially of a male member and a female member having a bore engageable over the male member, and a threaded member threadable in a partially threaded bore having an axis substantially parallel to the longitudinal axis of the male member, a portion of the partially threaded bore, for example one half, being threaded and formed in the male member and another portion being unthreaded and formed in the female member. Rotating the threaded member in one direction causes the female member to be displaced longitudinally relative to the male member to a desired position. The present invention can be used as an alternative to nuts and bolts for mechanical assemblies, by providing the male member with an enlarged head, or it may be used for mounting arms, pulleys, gears, cams and the like on a shaft.