A louver is a window blind or shutter with horizontal slats that are angled to admit light and air, but to keep out rain, direct sunshine, and noise. The angle of the slats can be adjustable, usually in blinds and windows, or fixed. Modern louvers are often made of aluminum, metal, wood, or glass. They may be opened and closed with a metal lever, pulleys, or through motorized operators. These systems serve to improve indoor day lighting

Louvers, in installations such as louvered doors or window shutters, are an attractive way to provide privacy and security while allowing for the free-flow of air on both sides of the louvers. Many people will buy louvered bi-fold doors for closets or position them as a screen for a dressing area. They are used for natural ventilation and temperature control.