It's about time for this thead to come 'round on the old guitar again.
Chiro75 said it best a month ago, "A lot of it has to do with how you present yourself and your overall demeanor."
At a busy airport check point, the guards "screen" literally hundreds of people an hour. They have a couple of seconds to make decisions about you. They basically judge the book by its cover.
If I know that I'm going to be judged by my appearance, by my language, by my simple actions, and by my demeanor, then I'm gonna put on the best show I can every time.
I never try to conceal my AFCK. I put it in the change tray and hand it to the guard. Only once has it been turned away. Fortunately, I was very early and the ticket counter was only a few hundred feet away, so I took it back and had it checked through as baggage. (The agents have envelopes for such things.)
My "secret?" Dress well, smile, and be very polite.
Several years ago, I waltzed through security with my AFCK as the guard one line over stopped a fellow with a smaller knife than mine. He was wearing a tee-shirt that said, and I don't make these things up, "I don't use 911, I use 9mm." That'll get the guard's attention. He was also being very loud and argumentative and using foul language. This is not the way to get through security. The guard had about two seconds to judge this book by its cover, and the cover spoke volumes.
If the guard does question your knife, the most important thing to do is this: do not make a scene. Do not attract attention. The guard's biggest personal fear is that someone will complain about him to his boss. One to many complaints and he looses a good job. He knows that if he turns you back, you might complain. But, he'll tell the boss that you were acting crazy, making threats, that the knife was huge and vicious-looking, etc., and the boss will write that complaint off. If, on the other hand he lets you through, then maybe the folks around you and behind you who saw the whole thing will complain that the guard let this threatening-looking knife through. If you draw a lot of attention to the problem, you put the guard in a no-win situation. In that situation, sending you back is the lesser of the risks for him.
Chuck