A plumb bob is a weight with a pointed tip that is attached to a string. The force of gravity
causes the weighted line to hang vertically, or plumb. Plumb bobs come in
different weights; the most common are 6, 8, and 12 ounces.
To mark a vertical line on a wall:
- Hang a plumb bob from a chalk-coated string almost against the wall
(ideally with a tiny gap). Secure the string at the top, near the wall,
with a nail.
- Steady the weight by hand until it stops swinging and twirling.
- Leave the weight to find its final position.
- Hold the weight against the wall and snap the string against the wall
to create a vertical chalk line.
- Remove the chalk line when no longer needed.