Dividers and compasses are two-pencil like pointers with sharp points connected by a central pivot joint. Usually made of steel, brass, nickel-brass or silver, they may be ornately engraved. They range in length from about 2 inches to 12. Dividers are used to repeat distances along a scale or measure at set increments on a drawing or map. Compasses are identical to dividers in basic design but since at least the 1300s one point could be used for scoring or for drawing an arc or circle. Compasses come in different designs primarily to accommodate different size circles. They include wing-compasses , screw-compasses, bow compasses, spring bow compasses, beam-compasses, which are two separate attachments devised by Leonardo da Vinci around 1492 to draw unusually large circles, pillar compasses, turn-about compass, and the pump-compass, which is a small pencil-like tube for drawing pinhead sized circles. As a drafting tool the sector provides results graphically and must be accompanied by a divider. The planimeter is a mechanical drafting and engineering tool that measures the area bounded by a closed curve. It consists of a rotating disc linked to a tracer that rolls against a cone to measure the area swept by the tracer.