502# is a kind of snap button. It is combined by an s-shaped spring and divided into four parts from the top down including cap, socket, stud and post. The female side part is composed of cap and socket. The surface of cap and socket can be carved with decorative patterns, and the middle of socket is a hole with two parallel springs. The male side part is composed of stud and post. The middle of stud is a convex dot which will be clamped tightly by the spring when pressed into the hole of socket, producing a combined force to fix clothing.