The book and boards must now be carefully lowered into the laying-press, keeping the relative position of book and boards unaltered, until the outer edges of

the backing boards are level with the cheek of the press. The inner side of the board is the straight one (A, Fig. 66), and this, in all cases, goes next the book; the sloping side (B) going towards the cheek. If the tyro finds the boards slip or change their position on the book, he may obviate this by expectorating slightly upon them before placing. The laying-press should now be screwed up with the press-pin as tightly as possible, and the workman, taking the backing-hammer in his right hand, proceed to "back." This is affected by hammering the back smartly down each side, so that a portion of the back of the outside sections is hammered down on the top surface of the backing boards and forms a clear and well defined groove.
This is an operation that looks very simple, but, as a matter of

fact, it requires both "nous" and knack. In the first place, the hammer must not be brought down edgeways on the portion of the book hammered down on the backing board, or it will cut through it. Next, although the book should be mainly struck down the sides, an occasional tap must be given to the middle, or the book will be "rabbit-backed," as shown in section at Fig. 67,

which is very objectionable. Lastly, the process must be so regular and careful; that no creases along the back of the section shall be seen when the volume is opened (Fig. 68). When the sheets are beaten in one direction, they should not be knocked back again. The hammer should be so manipulated that it always strikes away from the centre of the back, and that the course of the head should be circular.

The right shape of the back (in section) is about (Fig. 69) one third of a circle, or more, according to present taste.

We gave an illustration of a backing machine in a previous chapter; but its use is not to be recommended, as it is rather liable to cut the work.

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