A Brief History of Plumb Bob

			There is evidence that plumb lines have been used since the beginning of civilization. They seem to have been used by the Babylonians, ancient Egyptians, ancient Greeks and Romans to create precise vertical lines when plotting or marking the points of stars and planets. They still remain the most effective and accurate tools for determining the vertical in construction.
			Plumb lines through the ages
			The first plumb lines were made of stone. Ancient civilizations used plumb lines for many purposes, and they made their tools from materials that were readily available to them.
			Some early plumb lines were made from dense hardwoods such as ebony, oak, or ash. Since the plumb bob had to be symmetrical objects and have a rope attached to their axis of symmetry, it was important that the material from which they were made could be easily shaped. As technology progressed, the wooden plumb bob was later replaced by heavier metal varieties.
			In later centuries, plumb lines were cast from lead, hence the name of the plumb line. “lead” means lead in Latin.
			For centuries, the most common plumb bob material was a copper-tin alloy, better known as bronze.
			Some less common materials such as bone and ivory have been used for plumb lines, although these are usually antiques and may be purely decorative items not intended for everyday use.
			The death and rebirth of the plumb line
			The plumb line was almost forgotten by the invention of the spirit level, an instrument that has the advantage that it can detect both vertical (plumb) and horizontal (level) surfaces.
			As technology has advanced and better tools have been invented, this has given new life to the plumb line. As buildings were built higher and higher, masons needed a tool that could accurately transfer a point from one level to another, and so the plumb line lost its roughly oval beginnings, and necessity led to the ultra-thin point of the modern tool. we use today.
			Since then, plumb lines have been used to transfer points in the construction of tall buildings, so that when each level was erected, the structure remained vertical and correct.
			Plumb lines are still being used to check if Salisbury Cathedral is starting to lean!