_The causes of interfering_ lie either in the _shoeing_ (of the foot that strikes, as well as of the foot which is struck), in the _position of the limbs_, or in the _use_ of the animal. Horses that have the correct standing position do not interfere when they are properly shod; base-wide horses interfere sometimes; horses base-narrow down to the fetlock and toe-wide below that point interfere very frequently. Traces of unequal length, weariness, and shoeing at too long intervals favor interfering. In attempting to lessen or remove interfering, the horse must be most carefully examined with respect to the position of his limbs, his gait, and his shoeing, in the manner described on pages 90 to 92. [Illustration: FIG. 153. A right front shoe with nailless and narrow inner branch for a base-wide hoof. Suitable for horses that strike anywhere from inner toe back to the quarter.] If the cause is found to be the twisted position of a shoe, too wide hoofs, raised clinches, etc., nothing need be done further than to correct the shoeing; but if a faulty position of the limbs is the cause, we must ascertain the exact part of the hoof that does the striking, diminish the size of the hoof at that point, regulate the entire plantar surface of the hoof, make the shoe straight along the region that strikes,—that is, without curve,—and so fit it to the foot that one-third of the thickness of the wall will extend beyond the shoe. Where interfering is so pronounced as to produce serious injuries, we use a shoe with no nails in the inner branch (“dropped-crease” shoe) (Figs. 153, 156, 157). [Illustration: FIG. 154. Left hind shoe with interfering branch (ground-surface), for base-narrow standing position.] [Illustration: FIG. 155. The same (hoof-surface).] [Illustration: FIG. 156. Left hind interfering shoe without nail-holes in inner branch (“dropped-crease” shoe): _a_, side-clip.] [Illustration: FIG. 157. Right hind shoe for toe-cutters. The dotted lines indicate the distance that the wall projects beyond the shoe: _a_, side-clip.]