My favorite accessory is my template guide set....
Here's a picture of the 26inch Woodhaven original. Many of us have made similar jigs, but this is aluminum and pretty nifty. One thing worth noting is the long bottom bar of the jig gives room for clamps so that neither the workpiece nor the jig can move out of position. Cool.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.