Gait - Movement, or action, is the crucial test of conformation. The Terrier's legs should be carried straight forward while traveling, the forelegs hanging perpendicular and swinging parallel with the sides, like the pendulum of a clock. The principal propulsive power is furnished by the hind legs, perfection of action being found in the Terrier possessing long thighs and muscular second thighs well bent at the stifles, which admit of a strong forward thrust or "snatch" of the hocks. When approaching, the forelegs should form a continuation of the straight line of the front, the feet being the same distance apart as the elbows. When stationary it is often difficult to determine whether a dog is slightly out at shoulder, but, directly as he moves, the defect - if it exists - becomes more apparent, the forefeet having a tendency to cross, "weave," or "dish." When, on the contrary, the dog is tied at the shoulder, the tendency of the feet is to move wider apart, with a sort of paddling action. When the hocks are turned in - cow-hocks - the stifles and feet are turned outwards, resulting in a serious loss of propulsive power. When the hocks are turned outwards the tendency of the hind feet is to cross, resulting in an ungainly waddle.

Amplification
"Both forelegs and hindlegs should be carried straight forward when traveling." If a dog is moved on a loose lead at a moderate speed and is properly constructed, such movement is a realistic possibility. But a dog that is moved so fast that it naturally single-tracks, or pulls on the lead, or is being "strung up"' has no possibility of exhibiting correct movement. When going away, watch for the handler that strings the dog up to widen the rear. In profile, the Smooth should move with the greatest possible freedom (extension) of stride, reaching well out with the forelegs, driving with the rear, the legs swinging freely through a long arc. Faults are a short mincing gait which lacks extension and drive; hackney action in which the forelegs are lifted and curled rather than stretched forward; and "goose-stepping", an exaggerated extension of the foreleg with stiff, unflexed pastern, in which the foot can nearly touch the dog's chin. Be wary of the "over-angulated" dog that will surely be sickle-hocked. Judges should insist on movement on a loose lead. A tight lead can both create and disguise faulty movement.