To the uninitiated this seems an almost impossible feat. In reality, if done according to rule, it is not much harder than changing the under sheets. If the patient is heavy four people will be required to accomplish this deftly, two on either side of the bed. The sheets are loosened on all sides; the top sheets and the blankets treated in the same manner as when the bed clothes were changed; the under sheets are rolled tightly up to the patient's side (the roll being undermost). Using these rolls for support, the patient is moved to one side of the mattress; this side is then pulled to the centre of the bed, curving the mattress upwards; the fresh mattress is placed alongside, the patient lifted by the bed-clothes on to it, the discarded mattress removed, the fresh one drawn into place, and the patient lifted to the centre; the sheets are again unrolled and tucked in place.