A carpenter's square. It has a long side, about 49 cm, and a short side about 24 cm, and looks like an L shaped ruler. Also sashigane 指矩. It is used to take measurements, make right angles, and mark with India ink on a marking string *sumikake 墨掛. The carpenter's square is made of steel or brass and originally it was graduated in the shaku 尺, sun 寸 and ri 利 system of measurement. Today the metric system is used. Gradations on the frontside of old kanejaku were divided into 1.5 shaku to 1.6 shaku on the long side, and 7.58 sun on the short side. The gradations made on the back urame 裏目 outer edges are the square roots of those on the front side. These gradations are called *uragane 裏矩 or urajaku 裏尺. The gradations on the inside back of the arms are the same as on the front. They are called sashigane, kane 曲 or magarikane 曲矩. The back gradations were devised to handle the corners of the roof around the eaves.
left：urame 裏目 right：omote 表目