A couple of years ago one of my nieces was flying home from college for Christmas. There were no direct flights and one required a terminal change, so she passed through security in a couple of different domestic airports.

When she arrived home she was emptying out her backpack (which she carried on) and did a double-take.

At the bottom of her backpack was her suture kit, complete with scalpel, replacement blades, needles and a few other odds and ends.

Went through security just fine...