A die nut, also known as a thread chaser, is used for sharpening an existing thread. It is run over threads that may have been damaged or blunted over time to correct them to their original condition. It looks the same in appearance to a square or hexagonal nut. They are easy to use and can be operated using an ordinary box spanner or set spanner. They are available in various sizes, types and threads, with this information being engraved on their front surface or face.