This document discusses surgical drains. It describes drains as appliances that drain blood, pus, or air from the body. Drains are either passive or active. Passive drains rely on capillary action or gravity, while active drains use suction. Examples of passive drains include corrugated rubber and Penrose drains. Active drains like Redivac use suction. Drains have therapeutic, diagnostic, prophylactic, monitoring, or palliative indications and are used to continuously drain fluid, make diagnoses, prevent fluid buildup, monitor outputs, or provide palliative care. Complications can include infection, foreign body reaction, or injury to nearby structures.