Hi, I have a T key for when I'm volunteering on the F&WHR and was wondering what the third fitting is for (the round one)? Obviously whatever its for isn't actually in widespread use anymore, obviously assuming that it actually has a purpose? Thanks, Rob. oh and before anybody asks, yes I am allowed to have one, and no I wouldn't use it on any NR train. I can't say I won't carry it on an NR train because sometimes I have to get the train to Wales!