The plumb bob was a weight on a string. That was the whole tool. A pointed piece of brass or lead tied to a cotton line. You held the line at the top of the wall and the weight hung straight down and the string showed you where plumb was. Plumb means vertical. Plumb means true. The word comes from plumbum which is Latin for lead which is the same root as plumbing. The plumber and the plumb bob are cousins. The plumber follows the water. The plumb bob follows gravity. Both follow the thing that cannot lie.

The plumb bob did not need batteries. The plumb bob did not need calibration. The plumb bob needed gravity and gravity was always on. The laser level needs batteries and the batteries die and the laser goes dark and the carpenter reaches for the plumb bob because the plumb bob has never gone dark. The plumb bob has been working since the Egyptians built the pyramids. The pyramids are plumb. Four thousand years later the pyramids have not leaned because the Egyptian mason dropped a plumb bob and the plumb bob told the truth and the mason listened.

The plumb bob was personal. The mason carried the same plumb bob for thirty years. The brass wore smooth where the fingers held it. The point dulled from a thousand contacts with the floor. The mason did not buy a new plumb bob when the old one wore down. The mason sharpened the point and kept going. The plumb bob was not a disposable tool. The plumb bob was a relationship. The mason and the plumb bob agreed on what vertical meant and they never had to discuss it again.

You dropped the plumb bob from the top of the wall and waited. The bob swung. The bob oscillated. The bob slowed. The bob stopped. When the bob stopped the string was plumb. The stopping was the answer. The swinging was the question. The mason did not rush the plumb bob. The mason waited for the answer. The laser level gives the answer instantly. The plumb bob makes you wait. The waiting was the discipline. The discipline was the accuracy. The carpenter who waits for the plumb bob to stop is the carpenter who gets the wall straight.

Nobody uses plumb bobs on commercial jobs anymore. The laser level replaced it. The laser draws a line on the wall in green light and the line is plumb and the carpenter marks the line and moves on. The laser is faster. The plumb bob is slower. The laser works in any light. The plumb bob needs enough light to see the string. The laser has no weight. The plumb bob has weight and the weight is the principle. The weight is gravity made visible. The laser is an electronic line. The plumb bob is a physical law hanging from a string. There is a difference between a line and a law.

See also: Spirit Level, Cornerstone