Unique Plumb bob

A plumb-bob is a weigh 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 to ensure that constructions are "plumb", or vertical. What makes this item unique or unusual is that most plumb bobs are pointed at the bottom. This one is not.

How to Use a Plumb Bob
To use the tool, the string is fixed at the point to be plumbed. The weight, or bob, is then allowed to swing freely; when it stops, the point of the bob is precisely below the point at which the string is fixed above. (Note that the line must be hanging free to get an accurate reading.)
The plumb bob is useful in establishing vertical for a wall in construction or a doorjamb when hanging a door. A spirit level will also accomplish those tasks, but some jobs are much more easily done using a plumb bob. For example, you can locate fixtures or decorations in relation to an object or surface below (or above) using the plumb line. Once it is hung and still, the top and bottom points can be marked and used as guides. The plumb line in one place can be used to sight an object in another — a pipe, for example — for plumb.
Surveyors sometimes use plumb bobs for lining up points or transferring them. Excavation and foundation contractors rely upon the plumb line, and constructing a chimney the plumb bob can indicate whether a flue is running true vertical or veering off plumb.
Some bobs have pointed tips that can be bent by repeated use or abuse; if the point on yours is bent or out of alignment, replace it.
Plumb bobs may weigh as little as an ounce or as much as several pounds, depending upon the application. For most home toolboxes, I recommend having a single bob that weighs a few ounces. As is so often the case, it isn’t how fancy the tool is, but how well you use it.