Noun
a cord from which a metal weight is suspended pointing directly to the earth's center of gravity; used to determine the vertical from a given point
Source: WordNetplumb-line
The straightening board was created because of warped wood, and the plumb line came into being because of things that are not straight. Rulers are established and ritual and rightness are illuminated because the nature is evil. Xun Zi
However, based on abnormalities in plumb line deflection by the Andes in Peru, Pierre Bouguer had deduced that less-dense mountains must have a downward projection into the denser layer underneath. Source: Internet
They have been identified with two inscribed objects in the Berlin Museum ; a short handle from which a plumb line was hung, and a palm branch with a sight-slit in the broader end. Source: Internet