Marion, I have never used them. I have no need for them. If you use the right blade you shouldn't need to sand your cuts. If I have a miss-cut, I go back and clean it up with right side of the blade which has a burr on it from the manufacturing process.
After applying an oil and then a top coat of semi gloss spray lacquer, all my edges and inside cuts are smooth and shiny!
Now if your using a soft wood like pine, your edges and inside cuts will probably need to be sanded.
I do sand the back of the piece to remove the fuzzies, but never any inside cuts.