Slide the tip of this gauge through a hole, draw the gauge back until the hook hits the backside of the hole and you’ll be able to correctly determine the proper length of the Hi-Lok® fastener needed. Our grip scales serve two purposes. First, to measure the “grip length” of Hi-Lok® and Hi-Lite® pins, shear lockbolts, structural screws and bolts (the thick side of the tool). Second, to measure the thickness of materials to be fastened so that the proper length pin may be chosen (the thinner side of the tool). Made in USA.