The small section of the corner rounder is a perfect match for playing cards. It makes short cards or strippers invisible by removing the "flat" section of the edge.
I use fine sand paper to make short cards. There is likely a better method mentioned above, but it works for me. I scallop out my short card so the corners are unaffected and it is only short in the middle. Good for fine tuning also. 4-way nail buffer for buffing, but the the roughest section seems to remove a good amount of material and could likely be used for that too.