Nuts are a common fastener used in conjunction with bolts or threaded rods to achieve tightening and fixing functions. The nut is usually made of metal and has an internal threaded structure that matches the external thread of the bolt. The shape of the nut is usually hexagonal so that a spanner or spanner can be used to turn the nut. The internal thread of the nut is used in conjunction with the external thread of the bolt, and the nut is tightened with the bolt by rotating the nut. There are many different types of nuts, including ordinary nuts, nut gasket combinations, lock nuts, etc. Ordinary nuts are used for general fastening needs, the nut gasket combination provides a better sealing effect, and the lock nut prevents the bolt from loosening under vibration or load. Nuts are widely used in various fields, such as machinery manufacturing, construction, automotive industry and so on. The selection of the nut should be determined according to the specific application scenario and requirements, including the material of the nut, thread type, size, etc. The correct selection and use of nuts can ensure the fastness and reliability of fastening, thus ensuring the safety of equipment and structures.