Suction cups are simple devices made of flexible materials like rubber or plastic. They work by creating a vacuum when pressed against a smooth surface, allowing them to stick without any adhesive. This makes them useful for hanging items, such as shower caddies or decorative ornaments, on walls or windows. The effectiveness of a suction cup depends on the smoothness of the surface and the amount of air removed from underneath it. They are commonly used in various applications, including kitchen tools, car accessories, and even in medical devices for holding equipment in place.