Screws inevitably become loose; such common sense became things of the past. “Hard lock nut” exhibits a nearly perfect loosening prevention effect that does not cause screw rotation, and maintains high fastening force even under severe vibration conditions. Many of it have been adopted in many fields that emphasize safety, such as railway, bridge, machinery, construction, ship, and plants, to name a few. About 400,000 nuts are used in NASA’s rocket launcher, Shinkansen, and Tokyo Sky Tree. By using it, it is possible to maintain the initial axial force (fastening force), as a result, screw loosening and bolt breakage accident are prevented and labor cost, maintenance cost, enormous cost of complaints decreases dramatically. “Hard lock nut” continues to offer great total merit to companies around the world.