The wing nut, also called a trapezoidal nut, is a formwork fastening system accessory used together with a through-wall tie rod and a wing clamp. It features a trapezoidal thread design with a large thread contact surface, so the thread is not easy to strip 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 through-wall tie rods of the corresponding specification. It is mostly used in formwork projects such as building construction, basements, and water tanks, and can be reused many times.