![](https://www.horniman.ac.uk/media-collection/153/184/4809_1.jpg)
Right-angled carpenter's square (ju), consists of a vertical bamboo strip and a horizontal wooden beam of 1 traditional Chinese foot (chi) long, divided into 10 Chinese inches (cun), marked in black ink on bone attached at frontal side. This tool was used by Chinese carpenters to mark a right angle or a square and to check the accuracy of a 90-degree corner.