Plumb bob

A plumb bob, also called a plumb bob level or plummet, is a simple tool used to find straight up and down lines. It has a weight on the bottom with a point, and it hangs from a string. This weight can be made from stone, wood, lead, or other metals.

People have used the plumb bob since the time of ancient Egypt to help build things that stand straight up and down. This is very important when building walls, towers, or any structure that needs to be perfectly vertical. The plumb bob helps workers make sure everything is "plumb," which means straight up and down.

The plumb bob is also used in surveying. Surveyors use it to find the exact bottom point, called the nadir, of a spot on the ground. They use the plumb bob with other tools like levels, theodolites, and steel tapes to make sure their instruments are placed just right over a fixed spot or to mark where a new point should be put on the ground.

Etymology

The word "plumb" in "plumb bob" comes from the Latin word plumbum, which means "lead". Long ago, people used lead for the heavy part, called the bob, at the end of the tool. This gave us words like "plumb" and "aplomb", which mean being upright and steady.

Use

Plumb bobs help builders make tall structures straight. They give a straight up-and-down line that builders use as a guide. As buildings grow taller, the plumb bob moves up too, keeping the same center point on the floor below. You can still see marks on the floors of some old domes and towers that show where this center point was.

A plumb bob can also be used to measure how much something leans by attaching it to a scale. Long ago, people in Ancient Egypt used a tool with a plumb line to draw straight lines on walls. Builders in Europe used a triangle-shaped tool with a plumb line until the mid-1800s. Early skyscrapers used heavy plumb bobs hanging inside elevator shafts.

Sometimes, a plumb bob is placed in water or thick liquid to stop it from swinging quickly. Artists use plumb lines to find the center point of what they are drawing, helping them get the balance and shape just right.

In popular culture

After the game The Sims came out in 2000, a green plumb bob became its logo. In the game, this plumb bob helps show which character you’ve chosen and what they are feeling. Extra rings around the plumb bob in the game’s expansion packs can show special characters, like vampires, mermaids, and aliens.