B D Finch Jul 4, 2019:

@Tony I think you have funny-shaped turnips in your part of the world, not that I've ever seen many carrots the shape of the bobs called "carrot-shaped". However, I think you will find that different trades use different shapes of plumb bob. So, architects use long, narrow bobs and masons use short, squat bobs that may even be cuboid, and mechanics, apparently, use "carrot-shaped" ones. To each trade its vegetable.