Creating a powder horn strap staple ...

[RobD]

... from an armored electrical cable staple ...

[Ohio Joe]

Cool Rob!  

[Bigsmoke]

Man, after you twisted the staple, took it out of the vise and held your hand in back of it, it looked like you were going to lay it in your palm.
Whew!!
Thanks for not doing that.
With all that being said, here is another thought.
First, the weasel clause:  I am not much of a fan of woven horn straps or metal staples for that matter.  But I have heard that it is not a good idea to twist the staple like that, as it can accelerate the wear on the strap.  I guess with leather tabs on the strap it wouldn't be an issue, though.  I dunno, like I say I don't care for either item.  Much rather prefer a leather lace.
For the few staples I make, I use a piece of bailing wire .060" and cold bend it.  Works slick.

[amm1851]

I have used a hand forged nail, cold bent and sharpened at both ends.

[RobD]

i only use leather lace horn straps.

[Hanshi]

I've always made staples out of coat hangers.  They've worked really well for me so far.