You've seen them in the airport security line with their sleek, tiny suitcases -- those travelers who embark on multi-week vacations with just a 20-inch carry-on and a smug smile. How do they pack their lives into shoebox-size bags? Well, we've discovered their secret.

If there's one rule of thumb by which smart packers should abide, it's this: pack multi-purpose items. You can pack half as much (and say "sayonara" to airline baggage fees) if you've got the right travel gear. Start the slideshow to discover 11 must-pack travel essentials that do double duty on the road.