Grimsby/Cleethorpes Sunday League Football

Full Version: What is a plumb line?
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A plumb-bobA plumb-bob or a plummet is a weight, usually with a pointed tip on the bottom, that is suspended from a string and used as a vertical reference line, or plumb-line. The instrument has been used since at least the time of ancient Egypt[1] 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.
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