I worked as a supervisor for TSA for about a year. Never had a gun come through our little airport, but we had a bucket of various knives. We would also go through the terminal occasionally and check the potted plants for pocket knives people would stash and found a few.
Normally, we would offer to mail the knives we found to the owner, or even keep them in the office until they came back. Usually people would be so embarrassed they would just hand them over. I still have a couple of Swiss pocket knives and little Leatherman Mini keychain tools.
I was in charge of a small screener force in a little regional airport and made it about a year before I just couldn't look at myself in the mirror any more. I used about as much common sense and courtesy that the government would allow and I still hated myself for patting down old men in wheelchairs and little kids.
As a supervisor, I had to run tests on my people by stashing fake IEDs, hand grenades, large knives, and pistols in random bags to see how they did. My people were pretty decent and reasonably intelligent and found every single item. Except the IEDs. I would put them under a laptop or mixed in with other electronics and they never found a single one.
Of course now. they make you remove your laptop, so maybe now it is more effective. I worked there when it was still under the Department of Transportation.