Check Chains

I used them on rescues for safety and before someone showed me how to train a loose leash walk without, you know, yanking.  I didn't use them much, or for long, on any one dog, however.  If one or two tightenings didn't get the dog's attention enough that the dog would then respond to the chain zip (no tightening) - I knew I had to try something else.  I had a dog that came to me with a collapsed trachea and I was always careful about that.

If I see a choke chain on backwards, I just smile and say, "Did you know P means practice makes perfect?" If you walk your dog on the left, as most people do, the chain forms a P when it's going on right.

I still use a tightening collar for safety on scaredy rescues - a martingale if I can get it, or the chain if I have given all mine away at the time. 

Of course, most pet owners should be able to train a reliable loose leash walk using straight operant conditioning or even treat training.  But I know how easy it is to rely on a crutch or a "magic bullet" rather than put the time into it - heck, if the device is on right, being used right, and Fido is actually getting out for a walk rather than rotting in the back yard, I'm pretty happy.