Smooth Fox Terrier Standard and Amplification
as approved by The American Fox Terrier Club, Part 5

Forequarters - Shoulders should be long and sloping, well laid back, fine at the points, and clearly cut at the withers. The elbows should hang perpendicular to the body, working free from the sides. The forelegs viewed from any direction must be straight with bone strong right down to the feet, showing little or no appearance of ankle in front and being short and straight in pastern. Both fore and hind legs should be carried straight forward when traveling.

Forequarters standing: Left - Correct; Center - out at elbow, toeing in; Right - tied at elbow, toeing out.
Forequarters moving: Left - Correct; Center - weave and dish action; Right - paddling action.
Feet should be round, compact, and not large; the soles hard and tough; the toes moderately arched, and turned neither in nor out.

Hindquarters - Should be strong and muscular, quite free from droop or crouch; the thighs long and powerful, stifles well curved and turned neither in nor out; hocks well bent and near the ground should be perfectly upright and parallel each with the other when viewed from behind, the dog standing well up on them like a Foxhound, and not straight in stifle. The worst possible form of hindquarters consists of a short second thigh and a straight stifle. Both fore and hind legs should be carried straight forward in traveling, the stifles not turning outward. Feet as in front.
Hindquarters standing: Left - Correct; Center - cow-hocked; Right - open-hocked.
Hindquarters standing: Left - Correct; Center - cow-hocked; Right - open-hocked.

Amplification
The forelegs must be neither down in pasterns nor knuckled over forward of the pastern joint. This does not mean that the very "keen" dog should be penalized for leaning forward on their toes when on the alert. The feet should have short, well-arched toes with thick pads - the classic cat-foot. It is the highest of praise to say of a Smooth that it "has no feet," meaning that the toes barely project beyond the pastern when seen in profile. The rear legs should be well bent at the stifle, with hocks low to the ground, but angulation must not be excessive. Over bent stifles are weak in actual propulsive power and more often than not indicate "sickle-hocks."