Just wanted to note that only the newer TDI knives have locking sheaths. The older ones with the sharper handle angles don't have locking sheaths. It's a shame, too, because that's what I most liked about the old design. It was half way between a push-dagger and a straight fixed blade. I think there are after market options for retention sheaths for the old ones but they come with a standard friction lock from the factory. I wouldn't wear it on a vest because it's so obviously a knife but it makes a great concealable AIWB knife with a belt clip and a wedge on the sheath.