It’s important that the dog’s collar fits properly. Collars transmit the stimulus to the dog though a pair of prongs, and both must make contact with the dog’s skin. If you put the collar on too loosely, it won’t make contact, or will only touch occasionally. Too tight and there’s a chance of the dog developing sores. First, strap the collar high on the dog’s neck, not down near the shoulders. Take the receiver and try to move it. If it wiggles freely, the collar is too loose. If it doesn’t budge, the collar is too tight. You want it to move, but with some resistance. Then you know the points are making proper contact. Many collars come with short and long points. Short points are for dogs with short coats while longer points are necessary to reach the skin through longer or thicker hair.