The wing nut, also called a trapezoidal nut, is a formwork fastening system accessory used together with the tie rod and wing clamp. It features a trapezoidal thread design with a large thread contact surface, so the threads are not prone to slipping under load, and it locks securely, effectively withstanding the lateral pressure of concrete pouring and preventing formwork from bulging or shifting. It is generally cast or stamped, and its surface can be treated for rust protection. Tightening and removal are labor-saving, and it fits tie rods of the corresponding specification. It is mostly used in formwork projects such as housing construction, basements, and water tanks, and can be reused multiple times.