To properly measure the relative humidity in a slab, according to ASTM 2170, the RH reading must be taken at a depth of 40% of the slab thickness. But how thick is the slab? The traditional way to answer that question is to drill a hole through the slab, but that can compromise the underlying moisture barrier and does not allow for variations in slab thickness or corrugated pan profiles with elevated slabs. The portable CTG.600 Concrete Thickness Gauge from Taylor Tools solves those problems and allows drilling the hole for the RH probe by quickly and accurately measuring the thickness of concrete slabs without the need to drill, core, or excavate the slab. This hand-held, battery-powered device provides accurate (± 1/4 inch on a 6-inch slab), non-destructive readings in less than three seconds. It can measure concrete from 3.2 inches to 6 feet thick and results can be easily downloaded to a spreadsheet. For more information, go to www.taylortools.com.