The Starrett 237 Depth Gauge, Ruler Type, has a measurement range 0 to 6", a resolution (or smallest graduation interval) of a 1/64", with + 0.004" to -0.0035" of accuracy. The rule scale enables quick and easy measurements. The base is 2.625" long and is cut-out on one side to enable accurate readings. This gauge has a knurled nut to lock the gauge head into position for accurate readings. The unit has a hardened steel head and a tempered steel, machine-divided rule. Depth gauges are typically used in manufacturing, machining, and mechanical engineering. Depth gauges are precision measuring instruments used to determine the depth of any shape that has a step, groove, or slot. These gauges often take the form of sliders that travel on a measuring beam or rods, are moved to position by hand, and then adjusted with a calibrated screw. The base of the gauge rests at the top of the shape whose recession is to be measured, while the beam or rods extend to the bottom of the recession to determine the measurement. Gauge position is read from a graduated scale, dial, counters, or an electronic display.The L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company, founded in 1880, is headquartered in Athol, MA.