Topic summary
Plumb line
Extracted from the Wikipedia article Plumb bob.
Use
Ancient Egyptians used a plumb line attached to the top outer part of a tool resembling a letter E; when placed against a wall, the plumb line would indicate a vertical line. An archipendulum, an A-frame level with a plumb line hung from the vertex was also used to find horizontal; these were used in Europe until the mid–19th century. A variation of this tool has the plumb line hung from the top of an inverted T shape.