We once flew from Newark to Paris, then Paris to Amsterdam, and finally back to Newark from Amsterdam with me wearing a walking boot on my left foot. (About 9-10 weeks earlier, I had broken my ankle.) The boot had all kinds of metal clips on it. At Newark, they almost fought to be the one TSA member to just let me through. In Paris, no problem. But in Amsterdam, they asked if I could take it off. And I could tell by the tone of voice that it was an order, not a real question.