Louver (or louvre in British English, from French l’ouvert; “the open one”) is a frame with horizontal and vertical slats, which are angled to admit light and air, but to keep out rain, direct sunshine, and noise.
Louvers originated in the Middle Ages as lantern-like constructions that were fitted on top of roof holes in large kitchens to serve as ventilation while keeping out rain and snow. They were originally rather crude constructions consisting merely of a barrel. Later they evolved into more elaborate designs made of pottery, taking the shape of faces where the smoke and steam from cooking would pour out through the eyes and mouth, or into constructions that were more like modern louvers, with slats that could be opened or closed by pulling on a string.
Today Matthews & Fields builds wood louvers to be functional or decorative. Functional louvers have screening installed in the back, decorative louves have a closed back. Many shapes can be made, rectangles, round tops, arch tops, peaked tops, half rounds, octagons, triangles, and sunbursts. These are made with rough sawn cedar, smooth cedar, primed cedar, Koma(pvc) boards, and pine.