Abstract: A semi-friction and interlocking operative association is provided between a threaded shank portion and a nut or similar device threadly engaged thereon whereby unwanted accidental loosening of the shank portion and the nut will not occur. The apex or crest portions of the threads on both the shank portion and bolt portions are provided with resilient integral tines and the valley portions of the threads on both the shank portion and nut are provided with recesses into which the resilient tines may be seated upon proper alignment of the tines with the recesses. Still further, at least one or more flank portions of the threads on the shank are provided with randomly spaced beads for tight wedging seated engagement with corresponding thread flank portions on the associated nut threads and at least the nut thread recesses have swingable spring-type tines mounted therein for interlocking engagement with associated resilient tines on the bolt threads.