Pyramid skylights are generally found to be mounted on curbs on flat roofs. Available with a variety of slope or pitch options, rafter placement and glass size are determined by the geometry created by the relationships between sides and the desired slope. While the skylight is identified as a pyramid over a square opening, when built over a rectangular opening it is called a hip ridge skylight. Skylight pitch is normally determined by the architect's aesthetic intent, structural engineering requirements, or both. Multi-sided pyramids skylights, better known as polygon skylights, can be constructed over six or eight sided openings, as well as over irregular multi-sided openings.