Instrument that consists of two adjustable legs or jaws for measuring the dimensions of material parts. Spring calipers have an adjusting screw and nut; firm-joint calipers use friction at the joint to hold the legs unmoving. Outside calipers measure thicknesses and outside diameters of objects; inside calipers measure hole diameters and distances between surfaces. Hermaphrodite calipers, which have one leg bent inward and one straight leg ending in a sharp point, are used for scribing lines at a specified distance from a flat or curved surface. See alsomicrometer.