A cast is a protective shell made from plaster or fiberglass that is used to immobilize broken bones or injured limbs. When someone breaks a bone, a doctor will often put a cast on the affected area to help it heal properly. The cast keeps the bone in place, preventing movement that could cause further injury. Casts come in various shapes and sizes, depending on the injury. They can be colorful and even decorated, making them more fun for kids. After a few weeks, the cast is removed, and the bone is usually healed, allowing the person to return to their normal activities.