Tool - Plumb Bob
c. 1940Brass plumb bob, painted gold. String is wrapped at the top.
A plumb bob (sometimes called a plummet) is a weight, usually with a pointed tip, suspended from a string to determine a true vertical line, or "plumb" line.
The plumb bob is one of the oldest and simplest tools used in construction and surveying, consisting of a pointed weight attached to a string or cord. This specialized tool’s purpose is singular: to establish a perfectly true vertical line, known as a plumb line. It achieves this by harnessing the constant force of gravity, which pulls the weighted mass directly toward the Earth’s center. This reliance on a physical law ensures the resulting line is accurate for verifying uprightness across various building trades.
Reference: https://engineerfix.com/what-is-a-plumb-bob-and-how-do-you-use-one/
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Plumb bobs are typically made of brass, steel, or other metals, and are attached to a string made of cotton or nylon .To use the tool, the string is fixed at the point to be plumbed, and the weight is allowed to hang freely. Once the bob stops swinging, the tip indicates a precise vertical reference point. This makes it invaluable in construction for aligning walls, door frames, columns, and other vertical structures Surveyors also use plumb bobs to transfer points accurately from one level to another.
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