A cast is a protective shell made from materials like plaster or fiberglass, used to immobilize broken bones or injured limbs. It helps ensure that the bone heals properly by keeping it in a fixed position. Casts are typically applied by medical professionals after an injury is diagnosed through an examination or imaging techniques like X-rays. Casts come in various types, including plaster casts and fiberglass casts, each with its own advantages. Plaster casts are heavier but mold easily to the body, while fiberglass casts are lighter and water-resistant. Patients usually wear a cast for several weeks, depending on the severity of the injury.