Lumber is usually dried to a specific moisture content prior to further manufacturing or use. The amount of water in wood is usually expressed as moisture content and can be directly measured or calculated. The moisture content of wood is defined as the ratio of the weight of water in wood to the dry weight of the wood material. While lumber can be air-dried, the humidity in most localities prevents the lumber from reaching the moisture content required for the stability needed for interior use. A dry kiln is required to dry lumber to the necessary final moisture content and does so fairly rapidly. This publication discusses the design and operation of a solar-heated lumber dry kiln that is designed to be inexpensive to construct and simple to operate.