You’ll need a special ceramic rod to sharpen a serrated knife like a bread knife. You’ll gently rub the rod on the dip between each serration on the knife individually. Do this on both sides of the knife. After that, run the rod lightly along each flat side of the knife to wipe away any residue you may have ground off while sharpening the knife. For bread knives with significant dulling, you may need to use a harder (and more expensive) rod like a diamond-infused rod.