A recent TSA blog post cites several cases in which the agency's screeners stopped travelers from carrying guns or knives onto airplanes: "the passenger in Boston who had a steak knife in his carry-on bag; the El Paso passenger with a 6 ½-inch hunting knife in his carry-on bag; the LaGuardia Airport passenger who had eight rounds of 9 mm ammunition in his bag; the JFK Airport passenger who had a 6-inch butterfly knife in his bag; and the New Orleans passenger who had a loaded .380 caliber firearm—with a bullet in the chamber—in his carry-on bag." I'm not sure those eight 9mm rounds posed much of a threat, unless the passenger planned to hurl them at people. And as a commenter notes on the TSA blog, there is no indication that any of these passengers intended to harm anyone. But at least guns and knives are weapons (or potential weapons) that theoretically could be used to hijack a plane.
Not so the other contraband listed in the post: a "belt with [a] brass-knuckles buckle," a "cool western belt with bullets decorating the side," a "hand grenade belt buckle," or boots with "shiny bullets and handgun barrel heel." The TSA advises travelers to leave all such items behind to avoid confiscation. But what sort of threat do they actually pose? Brass knuckles themselves are banned from carry-on bags, and I suppose you could remove a set from your belt if you got into a brawl, but they do not seem like a practical weapon for a terrorist. The other articles of clothing feature either replicas, disassembled pieces, or inert versions of the real things that cannot actually be used to shoot anyone or blow anything up. The TSA's list of "prohibited items" includes "realistic replicas of explosives" and "realistic replicas of firearms," presumably to avoid confusion, but how realistic a weapon is a jeweled hand grenade attached to a belt or a gun barrel incorporated into a boot heel? "Here's an idea," says the first comment after the post. "Why doesn't the TSA start firing people who don't pay attention during the training, who don't know things they're supposed to know, and who don't know how to distinguish between a harmless object and a threat?"
Speaking of belts, if you have flown recently you probably noticed that the TSA is now requiring passengers at security checkpoints to remove their belts as well as their shoes. According to Salon aviation columnist Patrick Smith, the reason is that belts, even when they don't set off metal detectors, have been known to interfere with full-body scanners. Naturally, the rule is enforced even for passengers who are not selected for full-body scans and even at checkpoints where there are no scanners. For the sake of consistency. Furthermore, airline pilots such as Smith also have to take off their belts, even though they are entrusted to fly the very airplanes whose hijacking or sabotage the TSA supposedly is trying to prevent. And as Smith discovered, they have to take off their belts even if they opt for a pat-down precisely to avoid having to take off their belts.
Bruce Schneier observes that "European airports have made us remove our belts for years." Yet unlike the TSA, they do not make you take off your shoes. Go figure. Schneier says if you pull out your shirt tail to cover your belt you should be able to walk through with no problem, provided your belt does not set off the metal detector—as the one with the hand-grenade buckle probably would, so it's a good thing you followed the TSA's advice and left it at home.
[Thanks to Mark Sletten for the tip.]