I put all my pups on a chain at about 12 weeks, 5 mins the first time, then 10, then 20, you get the idea, once they will stay on a chain with no fight, I start leading them.
At first I use a "piggin string" if they fight it gets tight, if they don't fight it stays loose. It works pretty well. I got the idea from Delmar Smith.
Some dogs fight it at first, but a few mins a day, and they are walkin along with not "tug" on any lead. I can tie a dog in a rig with bailin twine.
I don't chain my dogs, or even bring them out of the woods on a lead, but I train all of them to "chains", and to a "leash". Mostly for the same reason as other guys. A lead broke dog won't kill himself in a snare, and you never know when you may have to chain a dog.