Post-and-lintel construction is the most common form of construction in developing countries because of its economy and ease of implementation. It is also called "stick building", because all materials are cut from natural trees or manufactured from bamboo or wood. The posts act as structural supports for the roof. They are usually spaced fairly far apart, with the height of the structure determined by the length of timber used. The lintels that span the gap between the posts provide the main load-bearing surface. They can be made of wood, which is commonly the case, or sometimes reinforced concrete. This type of construction is very economical because it does not require metal framing or cement for the foundation. The only material needed is fresh wood, which can be obtained by cutting down trees or shrubs. Sometimes old tires or other waste materials are used as lintels instead of wood. The post-and-lintel system was widely used in ancient Egypt for buildings as large as five stories high. It is also found in India, China, Indonesia, and Japan.