A press stud, also known as a snap fastener, is a two-piece fastening device commonly used in clothing and upholstery. It consists of a metal or plastic stud that is pressed into a round socket. The press stud is secured by pressing the two pieces together, which causes the stud to snap into the socket. The press stud is a popular choice for clothing and upholstery due to its ease of use and durability. The term 'popper' is often used to refer to press studs, as the sound made when the two pieces are pressed together is similar to that of a popping sound.