I had a great dog leash made out of climbing perlon, kind of a macrame, with a 'biner on one end and a hand loop woven in the other. And of course it's been stolen...so I'm not an idiot [thanks bill for not jumping on this], I can do this, but maybe I could use a couple of well placed hints. I've got quite of bit of retired 5mm or ?

Check out leather weaving techniques like a lariat weave (best) or a round weave (easy.) If you can find a scout troop they should have someone who teaches leather working. Or if there is a tack shop in you area they may have instructions or know where to point you.
Sorry I can't give you more than names to look for but it has been a while since I have done any weaving.

By the way the hand loop is called a eye splice and the biner is attached most likely with an end splice.

Thanks for the information, I now know 1000 percent more then I did before...I still think if I can tie a grapevine knot in the dark I can make a tri-colored dog leash in the light. There were just a few other things in life I thought I could do also...

Why not just a simple braid, or get a little fancier and use doubled strands, giving you six strands? Unless you have a real monster or one that like to chew, that should be more than enough.

I was at the docks where our local commecial fishermen berth and make repairs and watched a fellow tie up his golden retreiver with some 3/4" line. He was barely down in the hold before the dog had chewed through the rope and wandered down the dock. I was amazed how easily the mutt bit through the line.