Interior shutters usually hinge on either side of a window opening, and swing inwards to allow access to the window or to allow light to enter a room. Operable louvred shutters have louvres, or slats, that rotate open or closed to control light, visibility and airflow. Shutters that have operable louvres are described using different terms such as traditional shutters, California shutters, or plantation shutters which typically refers to the size of the louvre blade. Other interior shutters use stationary louvres that do not rotate (fixed louvres), solid panels that can be raised, recessed or flat, fabric inserts or tinted glass. Shutters can be configured in a single tier unit that has one shutter top to bottom of a window opening as well as multiple tiers. Multiple tier units feature separate shutters on each tier which allows the top shutters to be opened independently from the bottom shutters. Café type shutters refer to shutters that only cover the lower portion of a window. Full height shutters can be made with a horizontal divider rail which separates the upper and lower portions of the shutter. With operable louvred shutters this gives greater control as the louvres above the divider rail can be operated independently from the louvres below the divider rail. A tilt bar (rod) is used for adjusting louvre position and to keep them in a uniform position. Interior shutters can be constructed from numerous woods, which can be painted or stained, and a variety of synthetic materials. Interior shutters that are made to close tolerances are preferable for the best possible fit. When louvres or tilt bar (rod) become damaged, replacement kits for these damaged parts may be ordered online and are easy to install.