The German Type Plumb Bobs are weights, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is essentially the vertical equivalent of a water level. A plumb bob is a small piece of metal that weighs down a string attached to it to indicate plumb, which is an exact vertical position. Builders today consider the plumb bob a basic tool box item. The German Type Plumb Bobs are very efficient.