A few days back I discovered that I had a 5″ screwdriver in my computer bag. It’s been on every flight I’ve taken since 1997, maybe 50 screenings (including Washington National, Washington Reagan, San Francisco, Philadelphia and Baltimore). Nobody ever noticed.
Airline screening is a little like the lock on the back door of my house. It will keep honest people out, but a burglar would be barely slowed down by it.