Everybody knows you should keep a spare $20, $50, or even $100 bill tucked away in a back pocket of your wallet for emergencies. Problems where do you keep it where you won't see it and be tempted to spend it, or when you're like me and use a money clip. The solution is to go to a local drugstore or on Amazon and pick up a small aluminum keychain pill holder. I bought a set of 6 on Amazon for $7. They measure 1 7/16" X 33/64", and use an o-ring, claiming to be watertight. Take your emergency cash, keep folding it in half until i fits in the holder. Now anytime I'm out, I've got an emergency stash, hopefully enough to get me out of whatever jam I managed to get into.