A PLUMMET The Egyptians used a simple device called a Plummer in the quarrying of the huge stones they used to construct pyramids and other buildings. It was important that such stones had straight edges and square corners. The plummet shown here is made up of an A-frame and a plumb bob suspended from the peak of the frame. Because of the earth's gravitational pull toward its center, the cord supporting the plumb bob will always form a right angle with the earth's surface.