Many people believe that a death by hanging is the result of strangulation. This is not true. A death by hanging is the result of a broken or dislocated second cervical vertebra called the axis, which, if the hangman knows what he or she is doing, should sever the spinal cord, arrest blood pressure, and force the subject to lose consciousness, all in a matter of about two seconds. The brain death that follows can take as long as twenty minutes, but that won't be enough time to revive the Fox Terrier dangling off the edge of your front seat by the end of this custom leash, as shown here in a simple how-to from the late 1950s.
So simple in concept, but this is a design built on a couple of dubious assumptions. First the assumption that a small dog will sit obediently on the edge of a car seat in a moving vehicle just like a little human and not get all crazy and fiendishly paw at or try to jump out the window. And there's the far more critical assumption that a sudden stop wouldn't throw said canine off his ass and over the carpet, hind legs first, snapped at the neck and tethered by a leather strap to the car seat, twisted in a frozen grimace like a roasted duck hanging in the window of a poultry shop. The instructions tell us that this leash is attached to "a sponge rubber ball wedged between the back and the seat cushion," the human equivalent of which might be a rope tied around the driver's neck, hitched to the back of the seat's headrest at a length of about ten inches. Try texting and driving trussed up like that, I dare you.
Although primarily—and ironically—designed to prevent injury to a small dog who insists on riding shotgun, the caption touts the added bonus of protecting "the instrument panel from claw scratches." But if scratches on your dashboard freak you out that much, wouldn't it be more humane to hogtie your pets and toss them in the trunk, or cage and strap them to the roof of the car, Romney-style?