I have multi-carry rigs for my old Gerber Mk1 and Gerber Guardian. The set includes an elastic and Velcro ankle rig.
Both work fine. If you don't wear trousers.
Access is very difficult and, even, impossible with one hand. If you want to retrodress in 70s bellbottoms, you have a chance. The only place it might be advantageous is seated in a car.
It is ,also, difficult to access the knife surreptitiously.
Reminds me of a bloke I met who has a gunshop in Sydney. He used to wear a stainless S&W .38 Sp in an ankle rig. One day, he was held up at gunpoint by a man who wanted the contents of the safe (mostly handguns). The shop-owner was enraged and, foolishly, tackled the BG. They wrestled all over the shop while the victim tried to draw his S&W....without success. He just could not get at it with one hand.
Anyway, the BG escaped leaving his gun and jacket behind. The gun ,BTW, proved to be a replica and Malcolm (just remembered his name) was embarrassed that he had not realized this.
He doesn't wear an ankle holster any more.
For a backup knife, the ankle carry is a final resort, IMO. And if is the only choice, inverted carry is essential.
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Brian W E
ICQ #21525343