My dog is obedience trained. His problem is that he knows when the leash or long line are on and will mind, but gets stubborn when the leash is off.

I have heard mention correcting a dog many times in your articles. My question is what would a level 10 correction look like compared to a lower level correction? My dog is almost eighteen months old and grabbing by the back of the neck does not have the same affect as it did when he was a puppy. Most of the time he minds, but occasional he will be a knuckle head. He knows basic obedience and most of the time he will respond to me saying "no." Another problem that I have is that he knows when he is on the leash and will behave differently. I make him drag around a fifteen foot line most of the time but my I think that maybe he needs to have a line on him all of the time until he behaves. The problem with that is when I take it off he knows I can't get to him and that's when he does not listen.