They way it was put to me at the local airport is that once you present your knife or whatever for inspection, either in the tray or by magnetometer detection, you have surrendered it. I realize different airport security organisations probably interpret the rules as they see fit or you might get lucky and catch a guard who's capable of reasonable and individual thought. Pre-9/11 if you forgot you had a handgun in your briefcase you were arrested immediately, not given a chance to check the gun or put it in your car. Given the menacing nature of the average SAK, I guess you could just consider yourself lucky if all you had to do was surrender your property. Like some others on the forum, I think I'll just drive.

Ed