In architecture, an arch is the span of an aperture that is not supported by a lintel. The word "vault" comes from the Old French vaut, which means "covering," "scaffolding," or "trap." The Latin word for sky is cubitus, so a vault is literally a covering over your head. There are three basic types of arches: semicircular, pointed, and straight. Semicircular arches have two curves- one to the left and one to the right- and meet at the center point where they connect. They are used primarily as doorways because they provide support for a large area above the feet while still allowing light and air into a space. Due to their importance as entrance ways, many semicircular arches can be found worldwide- especially in churches and other religious buildings. They are formed either from single pieces of molding or from several elements joined together with mortar or screws. The amount of material used to create the arc varies depending on how thick you want the arch to be. If you make the curve thinner, the arch will be lighter and allow more light into the room. Pointed arches have one sharp edge and one flat edge.