After the shoe has been nailed on tight the toe-crack should be immobilized. The best method is by buried nails. Slots are burned or cut on opposite sides at a distance of an inch from the crack. With a spiral drill (see Fig. 218) bore a hole from a slot at right angles to the crack. Make a similar hole on the opposite side. Make the holes continuous by introducing a straight hot wire. The rivet may be an ordinary round wire nail which has been softened by bringing it to a yellow heat and allowing it to cool slowly. It is driven through and the ends firmly clinched. Such a nail is easily placed, need not press upon fleshy leaves, can not be stripped off or lost, and holds fast. The horse should stand on the foot while the rivet is being clinched. Two are sufficient for a complete crack (Fig. 217). [Illustration: FIG. 219. _A_, Vachette burning iron for making the two slots to receive the ends of the hook; _b_, shoulder; _B_, Vachette hook; _C_, pincers for forcing the hook into the wall.] A more rapid, though less efficient method of immobilizing a toe-or a quarter-crack is by the use of the Vachette hook. A special apparatus is required (see Fig. 219). The burning iron (Fig. 219, _A_) is brought to a yellow heat, its end applied to the wall so that the two ears are on opposite sides and equidistant from the crack, when it is pressed firmly till the shoulder (Fig. 219, _b_) touches the surface of the wall. A Vachette hook, the distance between the points of which equals the distance between the ears of the firing iron, is seized by the special pincers (_C_), pressed into the slots burned to receive it, and is then driven into the horn by compressing the pincers. At the toe these hooks are frequently stripped off by the heels of the opposite shoe (in hind feet). Free application of hoof ointment, and maceration of the horn by melting snow or mud tends to loosen them so that they often drop out. An efficient method of fastening either a toe-or a quarter-crack is by using a metal plate one-sixteenth (¹/₁₆″) of an inch thick, provided with four to eight holes for the reception of screws four- to five-sixteenths of an inch long. The plate is heated, bent to conform to the curvature of the wall and pressed against the horn till it burns a bed for itself, when it is screwed fast. It will not loosen (see Fig. 220, _b_). In every complete crack of the wall the growing down of coherent horn is favored by thinning the horn for an inch on both sides of the crack directly over the coronary band (see Fig. 221, _a_), so that any gliding movement between the sides of the crack below can not be transmitted through the thinned area to the crack in the velvety tissue of the coronary band. Cutting a “V” at the coronet acts similarly, but is less efficient. [Illustration: Fig. 220.