I work at a Govt facility, and after 9/11 they installed airport metal detectors. Put up signs that said, "No knives allowed". Every single time you came in the building, you had to pass through these detectors. Didn't matter that you only went right outside to get a paper out of the machine in direct view of the guards, you still had to go through the detectors. All pockets must be emptied before you pass through, and if the machine goes off, they wand you. I always keep a Victorinox Mini Swiss Champ in the 5th pocket of my jeans, and one day I forgot to throw it in the tray. Bingo, the machine didn't go off. Evidently, there's not enough metal present to set it off. So, I stopped throwing it in all together.
A few months later, they loosened up the restrictions, and now we can carry knives with blades up to 3". Still have to go through the detectors every single time you leave the building, but I don't worry about the little SAK at all. I just leave it in my jeans, and it never sets off the machine.