Plumb Bob
Also known as
Plumb Line, Plummet
Used for
Establishing a true vertical reference line by gravity — checking that a truss leg, banner drop, or scenic tower is perfectly plumb before it's locked off.
Trade note
"Plumb" comes from the Latin "plumbum" (lead), the metal traditionally used to weight the bob. Gravity does all the work: a freely hanging weighted point always indicates true vertical, no batteries or calibration required.
Direct answer
Plumb Bob is used for establishing a true vertical reference line by gravity — checking that a truss leg, banner drop, or scenic tower is perfectly plumb before it's locked off. It is also known as Plumb Line, Plummet. Trade note: "Plumb" comes from the Latin "plumbum" (lead), the metal traditionally used to weight the bob. Gravity does all the work: a freely hanging weighted point always indicates true vertical, no batteries or calibration required.
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