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.
- Hill, Donald R.; al-Hassan, Ahmad Y. "Engineering in Arabic-Islamic Civilization". history-science-technology.com. Retrieved 11 September 2016.