The key for your rental car can open up to 13 other rental cars, according to travel security expert Kevin Coffey. One frequent traveler reports returning to his rental car, opening the trunk and finding no laptop computer or luggage. Opening the car with the key revealed his maps and other stuff were gone too. He then discovered his car in the next aisle, a twin of the one he had just opened.

Solution: Be aware, don’t trust your locked trunk as much as you used to, and carry with you (or leave at home) what cannot be replaced.