This is a classic plumb bob (also known as a plumb line).
Craftsmen, carpenters, builders, and surveyors have used it for centuries. You hang it from the string and let gravity pull the heavy pointed brass weight straight down. It creates a perfectly vertical line, helping ensure walls, frames, and structures are straight and level.
The pointed tip allows for precise marking on the ground or surface. It’s simple, reliable, and doesn’t need batteries — which is why many still keep one in their toolbox today.
If your dad or grandpa had one, they probably used it for hanging pictures, building shelves, or major construction work.
