Reed level
![Water is poured into the center top of the reed grass. The total amount of water, as illustrated by A(100%), needs to be equally distributed across B1 and B2. Equal output at both sides indicates that the reed is horizontally leveled.](/Images/godic/202502/06/Reed-level2830.png")
A reed level is an Arabic invention for determining level for the purpose of construction. A hole is put through a long straight reed and water is poured into the center. When the flow out of both sides is equal, the reed is level. The device serves the same purpose as a spirit level.