Leather stitching.

[John Fenna]

As you pass the two needles onto one side you loop one around the other to form a half hitch which then pulls into the middle of the leather and is hidden. At least - that is how I was taught...
If a stitch wears through on the surface it will not unravel either side as the half hitch locks the thread.

 

[S.C.M.]

ohhh! that makes sense. So you sort-of tie an overhand knot with each stitch. I can see why that would hold very well! Thank you!

 

[Tengu]

Thanks for the advice guys...Guess Ill have to be patient and saddle stitch...