In architecture, a gargoyle is a carved stone grotesque, usually made of granite, with a spout designed to convey water from a roof and away from the side of a building thereby preventing rainwater from running down masonry walls and eroding the mortar between. Architects often used multiple gargoyles on buildings to divide the flow of rainwater off the roof to minimize the potential damage from a rainstorm. A trough is cut in the back of the gargoyle and rainwater typically exits through the open mouth. Gargoyles are usually an elongated fantastic animal because the length of the gargoyle determines how far water is thrown from the wall. When Gothic flying buttresses were used, aqueducts were sometimes cut into the buttress to divert water over the aisle walls.