I had a 3 x rescan of my hand luggage recently when leaving ICN. I had no idea what the issue was and more and more items were removed from my bag until they showed me on the screen what they were worried about. It looked like 2 small blades. I was also none the wiser until I eventually realised they were metal collar stiffeners I had left in the shirt I wore the previous day.
Lots of smiles and relief all round