Luggage locks can help keep your possessions from going astray. But they can turn on you, too, if you forget the combination.

"The bigger and busier the airport, the less gentle handlers are with our luggage," an etiquette expert told Newsweek.

In an airport’s sea of squat polycarbonate ... partitioned with a zippered mesh panel. The suitcase can open, well, like a trunk. This differs from a classic hard-sided suitcase, which has ...