A hydroculator is a sort of quilted device filled with a clay-like substance used for pain management and in physical therapy. It comes in different sizes to mold to various parts of the body. It is used by immersing it in hot water, until it becomes warm. Then it is typically wrapped in one or more towels and applied to a part of the body that can benefit from moist heat. As it molds to the body with comforting warmth and gradually loses heat, users can safely, and often will, fall asleep without the danger of getting burns as from some electric heating pads.