A sheet or web supported by springs in a metal frame and used as a springboard is called a trampoline. The three main parts of a trampoline are the metal frame for keeping the form together, the springs for extra bounce and the flexible web or sheet made of nylon for giving the structure an initial bounce effect. Trampolines also come with added features for safety such as fences. It is used either indoor or outdoor for fun for both children and adults. They can also be used for professional sports and in gymnastics.