The panel lines on most of the bindings before 1500 show evidence of having been put in with a tool which has been pushed along the leather, and not with a wheel. I have found that a tool guided by a straight-edge, and "jiggered" backwards and forwards, makes by far the best lines for blind-tool work. It should be borne in mind that the line is formed by the raised portion of leather, and so the tool should be cut somewhat as at fig. 98. This should leave three ridges on the leather. Blind tooling may be gone over and over until it is deep enough, and may be combined with various other methods of working. For instance, in tooling such a spray as is shown at fig. 99, the leaf would be formed by five impressions of the second tool, shown at A, the extremity of the impressions could be joined with gouges, the stalk and veining could either be run in with a fillet or worked with gouges. The grapes would best be worked with a tool cut for the purpose. One edge of all gouge or fillet impressions can be smoothed down with some such tool as shown in section at B. This has to be worked round the gouge lines with a steady hand, and may be fairly hot if it is kept moving. At C is shown a section of a gouge impression before and after the use of this tool. The ground can be dotted in, or otherwise gone over with some small tool to throw up the pattern.
Blind tooling can sometimes be used in combination with gold tooling.
In the fifteenth century the Venetian binders used little roundels of some gesso-like substance, that were brightly coloured or gilt, in combination with blind tooling (see p. 325). This is a method that might be revived.
What is known as "leather work" is a further development of blind tooling. This method of decoration has been revived lately, but not generally with success. "Leather work" may be divided into two branches; in one the surface of the leather is cut to outline the pattern, and in the other the leather is embossed from the back, while wet, and the pattern outlined by an indented line. Sometimes the two methods are combined. As embossing from the back necessitates the work being done before the leather is on the book, it is not very suitable for decorating books. Leather first decorated and then stuck on the book, never looks as if it was an integral part of the binding. The cut leather work, which may be done after the book is bound, and leaves the surface comparatively flat, is a better method to employ for books, provided the cuts are not too deep, and are restricted to the boards, so as not to weaken the leather at the back and joints. Much of the leather used for "leather work" is of very poor quality, and will not last; for modelling it must be thick on the side of the book, and for the book to open it must be pared thin at the joint, thus making it necessary to use a thick skin very much pared down, and consequently weakened (see p. 155). Another very common fault in modelled "leather work" is, that the two sides and the back are often worked separately and stuck together on the book, necessitating a join, and consequently a weak place in the hinge, where strength is most wanted. Again, in most modern "leather work," those who do the decoration do not, as a rule, do the binding, and often do not understand enough of the craft to do suitable work.