The main saw is used to cut the tree into sawn pieces. The technique of eliminating uneven edges and imperfections from sawn pieces is known as edging. Trimming is the process of squareing off the ends of lumber to create uniform pieces depending on market measurements. The final step in the manufacturing process is called finishing, which includes applying a protective coating to the surface of the timber. Wood is the most common material for building materials because it is easy to work with and durable over time. Wood also emits very little toxic gas when burned. As a result, there is a growing demand for wood products in the world today. Wood is harvested from trees that have grown naturally without any human intervention. Before they can be used as building materials, all raw logs must be processed into standard board shapes. At the moment, nearly half of all harvested trees are used for wood production. In general, wood is a term used to describe the fibrous tissue found inside living plants. There are several different types of wood, depending on their usage. Building-quality wood is used for houses and other permanent structures. It is usually found in large trees that have been exposed to the environment for a long time. Commonly used wood items include furniture, toys, and art supplies. Scrap wood is discarded branches and twigs that would otherwise be thrown away.