On the upper part there is a sliding plate—the so-called platen—which draws out on prismatic rails.
A second plate works on hinges at the side of the sliding (or draw-out) plate and can be pulled out to the left. This plate is used principally for colour blocking—the other plate for gold.
Blocking can be done in gold and colour immediately after each other, and if the plate is in duplicate, four impressions can be made in succession without having to take off and change the plate.
In the upper plate there are round borings for the gas burners or hot irons used for heating the press; the latter are out of date and do not produce a steady temperature.
It now remains to insert the article to be blocked in the press so that it will be blocked exactly on the spot required.
There are several ways of attaining this object, which are adopted according to the kind of work in hand. The surest way is to mark the place by pins.
Two large drawing pins are pasted upon pieces of cardboard, a second piece of board is placed over each one so that the head is embedded between the two pieces but leaving the points free. The gauges thus made are fixed with wax at convenient places, best on the middle line above and below the table but in such a way that they themselves are not touched by the plate. To prevent their falling off, a larger piece of cloth is pasted over them, always leaving the points visible. The surest preventive against falling off is to have screw-on gauges. A strip of metal having a slit in the middle can be screwed tightly to the table by means of a screw passed through the slit. At the end a steel point about 1/2 cm. long is riveted on. With this gauge the points can be adjusted to any position on the table as required.
All work not turned-in which requires repeat blocking, and all such as requires blocking in more than one colour, is "pinned on." On the other hand, covers which are finished after being once blocked on back or side which require no second impression may be adjusted with the angle gauge or blocks. Many make use of both at the same time. Such covers then have been turned in all round when being worked, whilst "pinning on" requires that the covers should not have been turned in.
The practical bookbinder who has to deal with turned-in covers frequently gets over the difficulty by making two incisions about 2 cm. apart with the knife upon the turned-in edge at the place where it should be pinned on, and opening out the material at the incisions, thus making a loose margin for pinning on.
For pinning on covers as well as backs, a template is cut from wrappers or thin board, which is adjusted on the cover and the register holes made with an awl. When pinning-on has to be done for blocking which has to be repeated very many times, the register points are strengthened behind with stiff paper to prevent them from breaking or tearing away and thus becoming inaccurate.