A gurney, known as a trolley in British meical context, is the U.S. term for a type of stretcher used in modern hospitals and ambulances in developed areas. A hospital gurney is a kind of narrow bed on a wheeled frame which may be adjustable in height. For ambulances, a collapsible gurney is a type of stretcher on a variable-height wheeled frame. It is usually covered with a disposable sheet to aid in preventing infections. The key value of which is to facilitate moving the patient and sheet onto a fixed bed or table on arrival at the emergency room. Both types may have straps to secure the patient.