U.S. Patent No. 4,887,543 (.pdf)
The world is a pretty forgetful place. We all leave our keys, our wallets and our umbrellas at restaurants every once in a while. Thanks to this patent, you'll never forget your umbrella again. Don't worry, it isn't a very difficult method, particularly after you've read the description that goes into exquisite detail. Of course, it does feel something like a reinvention of the wheel: in the end, the method described so carefully is just a coat check for umbrellas, to be used at the door of a restaurant/club/your house. The host takes your umbrella, gives you a keychain to be attached to your keys (which, of course, you'll never forget!) so that, should you forget about your umbrella, you know where to go to claim it when you go to unlock your car. Whew, now we can all sleep soundly without having to worry about getting our fancy dinner clothes any wetter in the rain!