In the discussion on Sneaking stuff onto Airplanes was a wee gem of inspiration:
"... by the time you've got to the security checkpoint you've already checked your bags in.
How can you put your pen-knife in the hold if your bagage has already been checked in?That forces people to subvert the system knowingly.
This shows yet another failure in their system. When the security check does fail, it doesn't fail gracefully enough. It compounds the failure by not allowing the average user to put himself in an acceptable state easily."

Yupe. I recall recently boarding a domestic in Chch, and finding they were x-ray screening, & I had left my (rather big) pocket-knife in my pocket.
My luggage was checked in, so I became the "bad-guy", and slipped the knife through the system (technique confidential). I sure-as-shit wasn't going to surrender it!

Why doesn't *someone* do this:

At San Jose, CA (SJC) airport, there's now a smallish metal drop box outside the security check area which has a supply of plastic bags and labels. You fill in the details like your address (including a credit card number), put your contraband item - pen knife or whatever - in the bag along with the labels, put the bag in the drop box, go through the security checkpoint undetained and cross your fingers.