This jig makes it easy to set the bit for routing flutes or dadoes. I simply drop the appropriate depth gauge into the channel, set my router on top and lower the bit until it touches the gauge. The base is an 8-in. square piece of 3/4-in. MDF. Two strips of 3/4-in. MDF on top create a channel for the gauges. To make the gauges, subtract the depth of the dado you want to rout from 3/4 in. For example, a 1/4-in.-deep dado requires a 1/2-in.-thick gauge.