If your working aerospace, get it calibrated and buy the cert. If your wrenching cars, couple it parallel and opposite a beam type torque wrench and set it to 100, pull the 2 down over your bench vise flat and have someone look at the beam and note when it clicks. There you go. There is a nut at the bottom of a clicker that can be turned against a very stiff spring that alters the click tension. Look up even cheap torque wrenches, most are pretty accurate, like +-5% at 100.