Serrations grip the material surface instead of the threads for easy installation and mild vibration resistance. The flange distributes pressure where the nut meets the material surface, eliminating the need for a separate washer. About half the strength of medium-strength steel flange locknuts, use them in light duty fastening applications, such as securing access panels. Height includes the flange.Zinc-plated steel flange locknuts resist corrosion in wet environments.