Cures for Loose Dadoes
Sloppy slots can be a headache -- here are three ways to mend them.
Offer One Solution
Use veneer or rip a shim of matching stock to fill the remaining gap, sanding, if necessary, to create a tight fit. Place the shim on the side where it will least likely be seen. For example, few people will ever look under a low shelf, so put the shim below it. Install a shim on the top side of a high shelf. Glue the shim to the shelf and dado wall, trim or sand it smooth, and you'll likely be the only one to ever know it's there.