A sightseeing trip with my parents included a stop at a landmark building where we were forced to go through a metal detector and send our personal items through an airport-style X-ray. They found a nail-clipper-sized knife in my father's backpack that he didn't know he had. I said, "Wow, I can't believe you spotted that," to the security guard, to which he replied, "We're professionals." They made my father leave the knife in an envelope that we could claim on the way out. When he pulled out the claim ticket with his keys on the way out, he realized he had an identical small knife on his key chain. Security wasn't the tightest, though they did think highly of themselves.