An instrument photo of a caliperused to measure the thickness or diameter of an object. It consists of a pair of movable metal or wooden arms with curved, pointed ends, hinged together; or, having a fixed and a movable arm on a graduated stock. see thumbnail to rightThe two kinds pictured here are among the most common types, however there are many others. A sculptor can take an exact measurements from a model with a caliper. Inverted measurements, as well as scaled enlargements and reductions can be obtained with calipers. see thumbnail to leftThese are proportional calipers. By tightening a wing-nut one can establish a vertex anywhere along the central section of this caliper's length. They can enlarge a measurement up to 5 times, or reduce one to as much as 1/5, from measurements taken from either an inside (negative) space or from a positive space.(pr. KA-lə-pər)Also see pantograph, pointing and pointing machine.