What is a plumb line?

A plumb line is a tool used for determining the vertical alignment or true vertical direction of an object. It consists of a weight, often made of metal, attached to a string or a wire. When the plumb line is held or suspended, the weight is free to move and will come to rest in a vertical position due to the force of gravity.

Plumb lines have been used for centuries in various fields such as construction, carpentry, surveying, and plumbing to ensure that structures are built vertically straight. They are also used in fields like geology to determine the depth of bodies of water, and in physics to demonstrate the concept of gravity.

In addition to the traditional hanging plumb line, there are also laser plumb lines that use a laser beam to project a vertical line onto a surface. These are often used in modern construction projects for accuracy and precision.