When it comes to obedience it is important that dogs understand the word NO, to us it means, what you just did is incorrect and go back to what you where doing, we utlize this for when a dog breaks Place, Down and Recall command. Meaning if you where in Place and get up, and you here the word NO, you go back to Place, if you are in a Down and you get up, and you here the word NO, you go back into a Down.