There are a lot of dado jig designs out there. They’ve all got some good features. I’m working on a modified version of the Never Fail Dado Jig. Its best feature is the knobs on the top.It gets it’s straightness from rails made of hardwood and works with a paired router bit/bushing. I think that the top where the knobs go was joined to the long side with pocket screws (can’t tell for sure from the pictures). I’d rather cut the whole thing from one piece of plywood and I don’t need a 40” wide jig.
I drew up a CAD drawing based on the pencil sketch modified for my needs. Here it is:
-- Doug - When all you own is a hammer, everything looks like a nail.