Pop rivets are fasteners used to join two or more materials together, typically made of metal or plastic. They consist of a smooth cylindrical body with a mandrel that is pulled through the body to create a secure connection. Once the mandrel is pulled, it breaks off, leaving a strong, permanent bond. These fasteners are popular in construction and manufacturing due to their ease of use and ability to join materials without needing access to both sides. They are often used in applications involving aluminum, steel, and plastic, making them versatile for various projects.