Well, in the case of The Perfect Leash what I custom ordered from Bold Lead Designs, you add a swivel between the collar and the body of the leash.
Yes, I did order a second custom leash, why do you ask? I have been searching for The Perfect Leash my WHOLE DOG-OWNING LIFE and having found it I was not about to be without backup. The Perfect Leash is a multi-function lead with integrated limited-slip collar. Configure it as a normal 6′ lead, and you have a toileting/normal walk leash. Take it down to its shortest length and it’s the PERFECT shoulder-leash to keep Siddy right where I need him for balance work. The swivel-less version is absolutely fantastic, but the addition of a swivel has made it even better, something I did not think could be done.
I will have to get pics of the Perfecter Leash in action, because all you dog owners will be all “Dang, I wish I had a leash that cool.” Helpfully, I have pointed you at the shop where you can get one!