Translations:AY Honors/Carpentry/Answer Key/92/en
From Pathfinder Wiki
A plumb bob is a weight on the end of a string. The weight will hang straight down and is used as a reference for a perfectly vertical line. It can be used in some places where a level cannot - such as in a place where there is no vertical surface to place the level against. For example, a carpenter may wish to find a place on the floor just below a point on a ceiling joist so he can construct an interior non-weight bearing wall there and then be able to tie it into the ceiling joist. In this case, the wall does not yet exist, so there is nothing to place a level against to measure for plumbness.