=The sharp edge of the plantar border of the wall should be broken away with a rasp until the relative thickness of the wall equals its absolute thickness.= (Fig. 97). However, in healthy hoofs, that is, in those whose _walls are straight from the coronet to the ground_, the outer surface of the wall should =never= _be rasped_. The only exceptions to this rule are those cases in which there is an outward bending of the lower edge of the wall, most frequent on the inner side wall and quarter. [Illustration: FIG. 97. Longitudinal (vertical) section of the wall at the toe: _a c_ is the absolute, and _a b_ the relative thickness of the wall. With _a_ as the centre, and the line _a c_ as a radius, a circle is drawn; the corner of horn in front of this circle and indicated by dotted lines is to be removed with the rasp.] With respect to the inclination of the ground-surface of the hoof to the direction of the foot-axis, as viewed from in front, the following facts are established: In the _regular_ standing position of the limbs (seen from in front) the plantar surface of a hoof is at right angles to the foot-axis, and the outer and inner walls are of equal heights. In the _base-wide_ position of the limbs the plantar hoof-surface is more or less inclined to the foot-axis, usually to a very small degree, and the outer wall is somewhat higher (longer) and more slanting than the inner. In the _base-narrow_ position of the limbs the plantar hoof-surface is more or less inclined to the direction of the foot-axis, usually quite considerably, and the inner wall is somewhat higher than the outer. The foot is observed from the side in order to determine the proper relation of the length of the toe to the height of the quarters. [Illustration: FIG. 98. An untrimmed hoof with an excess of horn (_a_) at the toe which breaks the foot-axis backward.] [Illustration: FIG. 99. An untrimmed hoof with an excess of horn (_b_) at the heels, which breaks the foot-axis forward.] [Illustration: FIG. 100. Hoof dressed and foot-axis straightened by removing excess of horn below dotted lines in the two preceding illustrations.]