Router Bit Depth Gauge You're all set to rout V-groove into a piece of expensive stock. How can you be sure the depth you've set is the depth the router will cut? Simple. Check it with this handy router depth gauge. The guide is clearly marked in 16ths from 1/8" through 1" ...you'll set and check 15 depths precisely, without wasting material and time doing it by "trial and error"