1. Expand the contact surface, reduce the stress concentration of fastening force on the fastened part, and prevent the fastened part from being damaged. 2. When the nut is tightened, the fastener will not be scratched. 3. Flower pads and spring pads can also prevent nuts from loosening. Because of the above performance of square gasket, it can effectively prevent water leakage and water seepage of building structures, play a role in shock absorption and buffering, and also have a good fastening and sealing effect, so it is still widely used in daily life. Now, square gasket is mostly used in construction sites. Among the screws with nuts, the gasket is mainly used to increase contact area, reduce pressure, prevent loosening and protect parts and screws. Gasket is a mechanical seal between two objects, which is usually used to prevent pressure, corrosion, and leakage of pipeline due to natural expansion with heat and contraction with cold. As the machined surface can't be perfect, the irregularity can be filled with gaskets. Gaskets are usually made of sheet materials such as pad paper, rubber, silicone rubber, metal, cork, felt, neoprene, nitrile rubber, glass fiber or plastic polymer (such as polytetrafluoroethylene). The gasket for a particular application may contain asbestos.