When showing your dog, the movement of your dog is very important. A judge can tell if your dog is structurally sound and in proportion just on its movement. The main pattern asked for by a judge is a triangle. A Triangle shows the rear movement when going away from the judge, the side movement or profile when moving across the top of the triangle and the front movement when coming back towards the judge.
One of the main problems we come across in movement is Pacing, also referred to as Ambling. Pacing is when your dogs front and back leg on the same side moves forward at the same time. The correct movement of your dog should be a Trot, when the front left leg and the back right leg move forward at the same, in a diagonal. In some larger breeds pacing is acceptable, check your KC breed standard under Gait / Movement.
A dog may Pace because its tired as this movement conserves energy. Some large animals such as the camel move in this way. It may also pace because it is being moved too slowly.
Structurally, your dog may Pace because it is too short in the loin or upright in shoulder. However, this is only marked as a fault in adults as puppies may still be developing.
Pacing can usually be rectified by the handler, by moving a little quicker, or a small lead correction.
Below are some of the terminology used to describe faults in movement.