calliper rule

calliper rule

n
(Tools) a measuring instrument having two parallel jaws, one fixed at right angles to the end of a calibrated scale and the other sliding along it
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014