Buoy, a floating case, used either for supporting a man in the water or for marking a channel, an anchorage, or a dangerous spot. Buoys intended for supporting human beings afloat are called lifebuoys, and are either of canvas lined with cork, formed in the shape of a ring, or of sheet-iron fashioned into an air-tight vessel, and often provided with a "flare-up," or torch, which spontaneously takes fire upon immersion in water. Buoys used to denote channels are of various shapes. As employed by the Corporation of Trinity House, spirally painted buoys mark the entrances or turning points of channels; single-coloured can buoys, either black or red, mark the right-hand side of a channel going in; chequered, or vertically-striped can buoys mark the left-hand side; and, if further distinction be necessary, right-hand buoys are surmounted by globular frames and left-hand buoys by cages. The ends of middle grounds are marked by buoys with horizontal rings of white, bearing or not bearing above them a staff, diamond, or triangle. Wrecks are marked by green nun-buoys, i.e. buoys shaped like two cones placed base to base. Anchor buoys are small buoys, of no special prescribed shape, dropped from a ship's side before the anchor is let go, to denote its position. This operation is called "streaming the buoy."