Rubber, though the most expensive of these materials, is the most resilient and takes the best grip on smooth pavement. A pad of rubber, wide enough to cover the branches of the frog alone, or the branches of the frog and the buttresses of the hoof, firmly cemented to a leather sole, constitutes the modern rubber pad (Figs. 145, 146, 147). [Illustration: FIG. 145. A light driving pad, gummed and stitched to a leather sole; seen from the ground-surface and in profile. Used with a seven-to ten-ounce short shoe. _a_, stitching; _b_, rubber bar under buttress and frog; _c_, leather sole.] The frog- and buttress-pad used with a short shoe is to be preferred to the earlier frog pad which takes a full shoe. _The advantages of rubber pads are_: 1. They prevent slipping upon asphalt and other smooth, dry surfaces. 2. They diminish concussion, and are valuable in the prevention and treatment of sore heels, dry and moist corns, bruised sole, and incipient side-bone. [Illustration: FIG. 146. Air-cushion pad, seen from ground surface and in profile. Suitable for light harness horses.] [Illustration: FIG. 147. A heavy bar-pad suitable for heavy harness and draft-horses on pavement. The short shoe may carry a toe-calk of medium height.] 3. They give frog pressure, develop the frog and tend to prevent contraction of the quarters and those lesions which may follow contraction, as corns, cracks of bars and quarters, laminitis of the quarters and thrush. _A rubber pad should not be used_: 1. In contraction of one or both quarters, when the frog is too much shrunken to bear upon the pad. 2. In lameness from well developed side-bones. 3. In navicular bursitis (“navicular disease”). 4. In thrush, or canker of frog or sole. Rubber pads, light, medium and heavy, are made in all sizes and are suitable for all classes of horses, from the light roadster to the heavy draft type. The short shoe with which they are used reaches the middle of the quarters. The pad surface (upper surface) of the ends of the branches should be bevelled to conform to the pad, and to hold it firmly against the frog and buttresses. The thickness of the shoe should equal two-thirds the thickness of the pad, so that when fitted one-third of the thickness of the pad shall project below the ground-surface of the shoe. The shoe should be provided with a strong toe-clip. With the heavy, thick pad of a draft-horse a low toe-calk may be used, but heel-calks should never be put on a short shoe. Pads are seldom necessary on the hind feet. CHAPTER IV. SHOEING HORSES THAT FORGE AND INTERFERE. A. Forging.