Found this heavy pointed brass weight in my dad’s old toolbox. It has a string attached. What is this?

6. Common Trades and Projects That Relied on Plumb Bobs
Plumb bobs were essential tools for various trades, including masonry, carpentry, and surveying. Masons used them to ensure that stone and brick structures were perfectly vertical, preventing future structural issues. Carpenters relied on plumb bobs for installing walls, door frames, and cabinetry, where precision was crucial.