The hopeless nature of the TSA quest to forbid weapons may be illustrated with a simple sheet of typing paper. Take a sheet out of your printer. Roll it up into a cone with a point on one end and a 2-3" wide base. Hold the wide base in your hand and (carefully) jab something with the pointy end.
The cylindrical body of your new paper "dagger" is fairly resistant to sideways pressure, while the point can do real damage if directed against soft tissues. The strength of a single paper sheet is limited, so two or three may be used for a stronger construction. A manila envelope would be stronger yet, as the two sides are connected and the paper is thicker.
A plastic binder would be stronger yet. If a material isn't pliable enough for rolling up, folding it into a three or four sides pyramid would work as well. The flared base end would act as a pommel, keeping the hand from slipping from the impact of a stabbing motion.
A sheet of paper can be a weapon. A terrorist can use it, as can a counter-terrorist. As long as TSA is focusing on weapons, they are missing the real weapons -- the human brains. ANYTHING can be turned into an offensive weaponized tool. Unfortunately, very few tools can be improvised be defenders quickly enough to make a difference. TSA policies are further stacking the deck in favor of hijackers.