Dovetail jig does an about-face as router guide
Your dovetail jig can do more than you think - it can also be used as a dado-cutting guide.
When I needed to cut dadoes for a bookshelf I was building recently, I hit upon the idea that my dovetail jig might serve double-duty as a dado-cutting guide. I just turn the dovetail template around so the backside becomes a straightedge for the router base. Once I square the workpiece to the straightedge, the dovetail jig's upper clamp holds it securely.
This single-clamp system, which takes up to a 13"-wide board, works much better than trying to align a straight edge with two clamps. For long boards, I support the back of the workpiece to keep it from racking and distorting the elevated jig.
— Martin Staebell, Batavia, N.Y.