Furthermore, we must give the nail that form which will insure its passing through the horn _straight_ and _not in a curve_; with this object in view, the nail is to be slightly curved so that the side which is turned towards the frog in driving (inside) will be a little concave, the opposite side convex (Figs. 130, 3, and 131, No. 10), since it is known that a straight nail always passes through the horn in a curve, and not only does not long remain tight, but is quite likely to _press upon and injure the soft tissues_ of the foot. (See also, Nailing.) At the point of the nail the _bevel_ is to be so placed that it will form a short one-sided wedge with the slanting side directed =from within to without= (Figs. 130, 3, and 131, _d_). A short bevel is suitable for nails that are to be driven low, while a long bevel makes it possible to drive them high. _The bevel should never form a hook; it must always be straight, should be sharp but not thin, and under no conditions incomplete_ (defective). [Illustration: FIG. 131. Machine-made horseshoe-nails (natural size) with a low, wide head for a fullered shoe. The last nail is shown from one border; the others from the inner face: _a_, head; _b_, neck; _c_, shank; _d_, bevel; _e_, point; _f_, inner face; _g_, outer face.] Machine-made nails, smooth, polished, bevelled, and ready for use, are, for many reasons, to be preferred to hand-made nails, though the latter are rather tougher (see Fig. 131). Before the shoe is nailed on it should be cooled and again carefully examined by a competent shoer, who should then place it upon the hoof, where it should be critically observed to see whether it really fulfils every requirement of a properly-fitting shoe. Afterwards, the least fault or defect must be remedied, and then the work of _nailing_ it begins. By nailing, the shoe is firmly and durably fastened to the hoof, in doing which the horn of the wall is spared so far as possible, the elasticity of the hoof borne always in mind, and wounding of the pododerm entirely avoided. =The nails must in all cases penetrate the white line= and pass through the wall in such a straight direction that they will appear neither too high nor too low upon its outer surface. In the first case there is considerable danger of pricking or close-nailing, and in the latter the nail-holes will tear out easily when the nails are being clinched. [Illustration: FIG. 132. Driving hammer.] In driving a nail, it should be held in the fingers as long as possible in the direction in which it is desired that it shall pass through the horn. A nail should be driven cautiously, with attention to its _sinking and sound_, and yet with enough force so that at each stroke it will penetrate from one-fifth to one-fourth of an inch. The power required at each stroke will depend upon the hardness of the horn and the size of the nail. Fearless driving and timorous tapping should not be allowed.