Triangular Level and Plumb Bob

This wooden triangle is part of the construction equipment that was used to ensure that all walls were smooth and perfectly aligned. The tool consists of three pieces: two of them were fixed together to form a right angle, while the third small piece serves as a crossbar. 

A limestone bob is suspended by a cord from the apex of the right angle. Placed against a perfectly flat wall, the string of the bob would fall between the two lines indicated on the crossbar.

From El Lahun. New Kingdom, 18th Dynasty, ca. 1550-1292 BC. Now in the Egyptian Museum, Cairo. JE 28782