It is hardly necessary to point out that in flexible work the cord on which the books are sewn will, if no corrective measures are adopted, be seen through the leather covering. When it is desirable that the cords should not be seen, the spaces between the cords are leveled up with paper so that the back presents a smooth appearance. The leveling up is much easier when the sewing is done with strong tape instead of cord.

When several books of the same size are to be bound, they are usually sewn in the one stack. The cords, which are kept sufficiently long for the purpose are then drawn out between the volumes and cut off so as to leave about It in. of cord projecting at each side of the back, a three band book having thus half a dozen ends. A few experiments in sewing wiII very soon demonstrate the fact that the kettle stitches pull the head and tail of the book together, and the thread swells out the middle. Care must be taken, therefore, that the kettle stitches are not pulled together too tightly, and the swelling must be counteracted by frequently beating down the back with a heavy folding stick. Attention must also be paid to the thickness of the thread used in sewing; when the sections are thin, the thread must be thin.

Overcasting is used when a number of single leaves have to be bound into a book, the plan being as follows: Having ascertained that the pages follow each other in proper order, the book is knocked up carefully at the head and the back and placed in the lying press between two boards, the back projecting about 1 in. above the pressing boards. The back is roughed with a saw and sawn in, after which thin glue is brushed over the back, and the book is left to dry. When dry, the book is pulled apart in sections, each section consisting of eight or sixteen pages, according to the size and other characteristics of the work. Each section is then over sewn along the back, the thread being fastened off at the end that is, at the head or foot of the page. This is known as overcasting; after this the sections are hammered lightly to embed the thread. This operation must be performed carefully, or the thread will be cut. Then these sections are sewn in the ordinary way, like other books. The first and the last two sheets of a book generally are overcast to lessen the possibility of their being torn away, by the weight of the covers, from the other sheets.

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