compass divider

Divider, instrument for measuring, transferring, or marking off distances, consisting of two straight adjustable legs hinged together and ending in sharp points. It is used principally in drafting for the accurate transfer of dimensions from a measuring scale and in machine shops for scribing lines on surfaces, usually machined, with dimensions taken from a ruler. A compass is essentially a divider in which one of the points has been replaced by a pencil or other marking device. The compass is useful for scribing circles or arcs of circles; it usually includes a scale to indicate the radius of the circle being scribed.