Commercial wood flooring is typically categorized into three parts: solid hardwood, engineered hardwood and locking hardwood floors. Solid hardwood uses planks that come from a single piece of wood, and can be repeatedly sanded to last for years and must be nailed or stapled to a wooden sub-floor. Engineered floors are made by fusing together layers of hardwood for extra stability. They can sit nearly anywhere in a facility because they can stand up to higher levels of moisture and humidity and are designed for installation over concrete. A locking, or floating floor is an engineered floor with a locking tongue-and-groove system that minimizes installation costs by eliminating nails, staples, and glue.