The principle of surgery is actually the principle of leverage, whose lever is a steel plate and whose fulcrum is the rib cage of the thorax. Theoretically, any kind of deformity can be corrected with the help of leverage, but in practice it is not simple. This is mainly related to the position of the plate and the special structure of the body. In NUSS surgery, the plate is located between the sternum and the heart, and the plate travels almost entirely in the thoracic cavity and mediastinum. This special location and structural peculiarities make it impossible for the operator to change the shape of the plate as many times as necessary, as in the case of inanimate test subjects. During the real operation, every time the plate passes through the mediastinum, there is an additional risk of heart damage, so the design of the plate must be completed before it is placed in the body. The design of the steel plate is primarily a curvature design. Such curvature must meet the needs of the thoracic deformity curvature. Theoretically, such a design should not be too difficult, but in practice it is not, mainly related to the following factors: (1) the specificity of the location of the depression. Most patients with funnel chest have depressions that are not symmetrical from left to right, and asymmetrical depressions require asymmetrical plate curvature; (2) the difference in the extent of depressions. Patients with more limited depressions require different plate curvature than those with wider depressions; (3) the specificity of the thoracic structure around the depression. Since this area is mostly used as the pivot point of the plate, its position and strength will affect the design of the plate. It can be seen that if a “U” shaped plate is put into the body in a uniform manner during funnel chest surgery, most of the time there is no way to obtain satisfactory results. This requires the surgeon to design each patient carefully for each deformity. However, the design of the plate places special demands on the design of the plate because there is a flipping process and the plate is not placed exactly against the inner wall of the thorax after placement. In order to have a perfect design, in addition to the above factors, the design can be done with the help of some geometric principles to obtain unexpected results.