These are the sets of sandpaper letters and numbers I made for Naters when I had use of an Ellison die cut machine.. I put vowels in red, consonants in blue and the numbers in green. I know this is what i've seen made commercially, so i just followed it. I used coarse sandpaper (about 5 sheets). Then I used my xyron to put sticky on the back and mounted the letters on 3"x4" pieces of cardstock. Cost very minimal.