Is a napkin that fits over your sleeve, so you can wipe your face with your forearm, as is so natural to do. It would be great on picnics, or at those stand-and-eat parties where your hands are already full. I would love to see them introduced at a formal dinner party too. Wouldn't that be splendid?
Zubie says this is fact an old invention--the accountant's sleeve, used to keep ink off the pen-and-ink writer's actual sleeves. I say we can bring this back into the 21st century, and into our table manners.
Get out your sewing machines!