Description: Edge inspection, using the optical gap method. Blades are slanted on both sides with insulated handles. Designed for precision layout and measurement work. Uses: Detect the flatness of plates, leveling rulers, machine tool work platforms, guide rails, and precision workpieces. Hold the blade edge perpendicular to the surface of the workpiece and check in the longitudinal, transverse and diagonal directions. During inspection, if the edge and plane of the workpiece are weak and uniform, the flatness of the workpiece is acceptable; if the intensity of the incident light is different, the plane of the workpiece is not uniform. A feeler gauge can be inserted at the edge of the blade and workpiece. The error of flatness can be determined according to the thickness of the feeler gauge. Specification: Material: Steel+Plastic Size Chart: 75mm: 76x11x34mm/2.99x0.43x1.34inch 100mm: 96x13x38mm/3.78x0.51x1.50inch 125mm: 124x10x34mm/4.88x0.39x1.34inch Package Includes: 1x Machinist Layout Edge Ruler Note: 1. Please allow slightly error due to manual measurement. 2. Due to the difference between different monitors, the picture may not reflect the actual color of the item. 3. Wish you a wonderful on-line shopping!