0.001 Dial indicator. Checkrod bolts the proper way, because sometimes torque readings may vary. Using the stretch factors supplied by rod bolt manufacturers, this stretch gauge offers a highly accurate way to measure torquepre-load. With a special, high-tension spring, this gauge remains conveniently positioned on the bolt during tightening, with adjustabilityfor bolts up to 2.75" long. Simply position the stretch gauge over the length of the rod bolt before applying torque, take a reading, and record it. Then torque down tothe proper torque setting, andtake another reading with the stretch gauge. Calculate the difference and check the manufacturer's specification.