I have a jig patterned after one made by Woodhaven. Woodhaven has some neat stuff. I have a lot of tools, including a metal mill, so I can make my own versions of a lot of a lot of jigs.
This jig is foolproof - works every time, because you set the jig off the actual piece of material to fit into the dado. One side is fixed; the other moveable. You put the shelf, or whatever, against the fixed side and just move the other side until it just touches the shelf. Rather than explain it, here's a link to the web page with the instructions: Woodhaven Dado Jig. I can set up my jig a lot quicker than trying to adjust my stack dado to a perfect fit.
This jig is foolproof - works every time, because you set the jig off the actual piece of material to fit into the dado. One side is fixed; the other moveable. You put the shelf, or whatever, against the fixed side and just move the other side until it just touches the shelf. Rather than explain it, here's a link to the web page with the instructions: Woodhaven Dado Jig. I can set up my jig a lot quicker than trying to adjust my stack dado to a perfect fit.