Inside the wall, wooden beams called "nuki" are attached between vertical poles. These "nuki" walls are very ingenious. The poles and "nuki" are all combined using tongue-and-groove joints, and reinforced with wooden wedges. This means that all the poles touching the wall are fastened onto the "nuki." This kind of wall is called "tairyoku heki," or a durable wall, and is actually very strong against earthquakes. On the surface of this kind of wall, a siding is fastened onto the poles, which makes the building structure even more durable.