On the subject of aircrew knives, when I was instructing on 2 Sqn at Shawbury we had a visit from some ATC cadets - seated in our crewroom and answering their questions, I felt something touch my leg and heard a soft 'click'. I waited a couple of seconds and then glanced down to see the little sh*t next to me had undone my knife and then realised he couldn't steal it because it was still attached.