A Grade 8 nylon lock nut, also known as a nyloc nut, is a type of nut designed to resist loosening from vibrations or torque. It features a nylon insert that deforms when tightened, creating a locking action that grips the bolt and prevents it from backing off. These nuts are commonly used in applications with high vibration, such as automotive and industrial settings. While repeated use can degrade the nylon insert, Grade 8 nylon lock nuts are generally considered reusable.