A plumb-bob.

A plumb-bob or a plummet is a weight with a pointed tip on the bottom that is suspended from a string and used as a vertical reference line.

This instrument has been used since the time of the ancient Egyptians by bricklayers, masons, and carpenters to ensure that their constructions are "plumb", or perfectly upright. In the Physical sciences Quality assurance, and Engineering, Measurement is the activity of obtaining and comparing physical quantities Ancient Egypt was an Ancient Civilization in eastern North Africa, concentrated along the lower reaches of the Nile River in what is now The craft of stonemasonry has existed since the dawn of Civilization - creating Buildings structures and Sculpture using stone from the earth It may also be used in surveying to sight a point on the ground that is not readily visible. Surveying is the technique and science of accurately determining the terrestrial or three-dimensional space Position of points and the distances and angles between Small plumb bobs are included in the kits of various instruments such as levels and theodolites. A theodolite ( is an instrument for measuring both horizontal and vertical Angles as used in Triangulation networks They are used to set the instrument exactly over a fixed datum marker, prior to taking fresh readings. This article describes a concept from Surveying and Geodesy. For other meanings see Datum (disambiguation.

Etymology of the name

The plumb in the name plumb-bob comes from the fact that such tools were archetypically made of lead (Latin plumbum). Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly The adjective plumb developed by extension.

Use

Up until the modern age, on most tall structures, plumb-bobs were used to provide vertical datum lines for the building measurements. A section of the scaffolding would hold a plumb line that was centered over a datum mark on the floor. As the building proceeded upwards the plumb line would also be taken higher, still centered on the datum. Many cathedral spires, domes and towers still have brass datum marks inlaid into their floors, that signify the center of the structure above. A spire is a tapering conical or pyramidal structure on the top of a building particularly a church Tower. A dome is a common structural element of Architecture that resembles the hollow upper half of a Sphere. Towers are tall human-made Structures that are always taller than they are wide usually by a significant Margin.

The early skyscrapers used heavy plumb-bobs hung on wire in their lift wells. The weight would hang in a container of oil to dampen any swinging movement, functioning as a shock absorber. A shock absorber in common parlance (or damper in technical use is a mechanical device designed to smooth out or dampen shock impulse and dissipate

Often, figure drawing students will also make use of a plumb line to find the vertical axis through the center of gravity of their subject and lay it down on paper as a point of reference. Figure drawing is an exercise in Drawing the human body in its various shapes and positions Reference Point is the first album by Acoustic Alchemy for jazz label GRP and their fourth album overall The device used may be purpose-made plumb lines, or simply makeshift devices made from a piece of string and a weighted object, such as a metal washer. This plumb line is important for lining up anatomical geometries and visualizing the subject's center of balance.

References

• 60 oz. Plumb Bob.
• String Line and Plumb Bob.

This article about an engineering topic is a stub. Engineering is the Discipline and Profession of applying technical and scientific Knowledge and You can help Wikipedia by expanding it.