Valuable books are either trimmed at the front and at once backed or they may be backed before trimming. This is generally done with bulky books, as they are liable to throw out a section, and this danger is lessened by backing first. The work of backing remains the same. If the fore-edge has already been trimmed, care must be taken that the grooves do not suffer during trimming after backing. One way of effecting this is to lay the book on a special cutting board with the edge up to the groove, or by making use of the arrangement on the clamp already described, and adjusting the groove of the book to the blocks fixed on the clamp.
Should the fore-edge not have been cut, the book must again be knocked straight after backing; to do this a strong cord is tied round the book about 1-1/2 cm. from the back, the book is then laid upon a firm bed, and the back again knocked straight; this work is called "tying up."
Fig. 42—Backed book arranged for trimming.
It facilitates the work if the book is taken up and lightly held in the left hand whilst the right holds the hammer and knocks the round inwards until the book is once more square.
The squared book is now trimmed, and it is not until the trimming is finished that the cord is loosened.
In pressing, several volumes of the same size can be done in the hand press at one and the same time.