This seems to be the one of the most common questions asked about gymnasium floors. These gaps are referred to as intermediate expansion spaces or washer rows. Wood flooring is a material that expands or contracts when moisture is absorbed into or evaporated from the flooring. These spaces allow the flooring to move incrementally across the floor in smaller units as opposed to one wide unit moving back and forth at the perimeter walls. The term "washer row" is used because of the method that was used to keep the expansion space open until the flooring was nailed. As the installers would nail the flooring, they would use a thin metal washer between the flooring strips, as needed, to create an intermediate expansion space in the rows of flooring. Newer methods of creating this gap have been utilized by using a nylon string or "weed eater" line that is removed as the flooring is installed.