A is a door, window or room divider used in traditional Japanese architecture, consisting of translucent (or transparent) sheets on a lattice frame. Where light transmission is not needed, the similar but opaque fusuma is used (oshiire/closet doors, for instance). Shoji usually slide, but may occasionally be hung or hinged, especially in more rustic styles. Shoji are very lightweight, so they are easily slid aside, or taken off their tracks and stored in a closet, opening the room to other rooms or the outside. Fully traditional buildings may have only one large room, under a roof supported by a post-and-lintel frame, with few or no permanent interior or exterior walls; the space is flexibly subdivided as needed by the removable sliding wall panels. The posts are generally placed one tatami-length (about 2 m or 6 ft) apart, and the shoji slide in two parallel wood-groove tracks between them. In modern construction, the shoji often do not form the exterior surface of the building; they sit inside a sliding glass door or window. Shoji are valued for not setting a sharp barrier between the interior and the exterior; outside influences such as the swaying silhouettes of trees, or the chorus of frogs, can be appreciated from inside the house. As exterior walls, shoji diffuse sunlight into the house; as interior partitions between rooms, they allow natural light deep into the interior. While shoji block wind, they do allow air to diffuse through, important when buildings were heated with charcoal. Like curtains, shoji give visual privacy, but they do not block sounds. Shoji are also thought to encourage a home's inhabitants to speak and move softly, calmly, and gracefully, an important part of the ethos behind sukiya-zukuri architecture. Sliding doors cannot traditionally be locked. Shoji rose in popularity as an integral element of the shoin-zukuri style, which developed in the Kamakura Period (1123–1333), as loss of income forced aristocrats into more modest and restrained architecture. This style was simplified in teahouse-influenced sukiya-zukuri architecture, and spread to the homes of commoners in the Edo Period (1603–1868), since which shoji have been largely unchanged. Shoji are used in both traditional-style Japanese houses and in Western-style housing, especially in the washitsu (traditional Japanese-style room). The traditional wood-and-paper construction is highly flammable. Construction Frame The shoji frame is a panel called a . It is assembled from interlocking laths of wood or bamboo called kumiko. ""