page_title: Plumb bob
section_title: Etymology
hierarchical_section_title: Plumb bob / Etymology
caption_attribution_description: English: →This file has been extracted from another file: Cassells' Carpentry and Joinery.djvu
context_page_description: A plumb bob, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is a precursor to the spirit level and used to establish a vertical or horizontal datum.
  The instrument has been used since at least the time of ancient Egypt to ensure that constructions are "plumb", or vertical. It is also used in surveying, to establish the nadir with respect to gravity of a point in space. It is used with a variety of instruments to set the instrument exactly over a fixed survey marker or to transcribe positions onto the ground for placing a marker.
context_section_description: The "plumb" in "plumb-bob" comes from the fact that such tools were originally made of lead (Latin: plumbum, French: plomb). The adjective "plumb" developed by extension, as did the noun "aplomb," from the notion of "standing upright."
caption: A plumb rule from the book Cassells' Carpentry and Joinery
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