A support in the form of either pieces of material cut to the width of the spine or a single piece which extends to the height and width of the spine, or, in the case of longstitch bindings, a guard or full cover wrapped around the spine of a bookblock, and through and to which the gatherings are sewn. The materials used include cartonnage, parchment, leather, horn and wood. Pierced supports, as the materials used indicate, can either be rigid or more or less flexible. Entire bookblocks were sewn through pierced supports, often using patterned sewing, and they should not be confused with the sewing restraint technique in which the thread from the outermost gathering at each end of the bookblock only was sewn through the supports in order to prevent the gatherings sliding off the ends of the sewing supports. On some longstitch bindings sewn through full covers of cartonnage, the sewing was reinforced by the addition of pieces of thin, flexible parchment or leather placed on the outside of the covers which were intended to prevent the thread from tearing through the cartonnage. These are usually so thin and flexible that they could not have been used as supports on their own and can safely been described as longstitch reinforcements. Where they are thick and stiff, they should, however, be described as pierced supports. It may not always be easy to distinguish which is which.
Double or triple supports will consists of multiple elements across the spine of a bookblock, creating in double supports upper and lower elements, and in triple supports, upper, central and lower elements. Many double supports were created out of single lengths of animal skin cut across the central portion to create the double or triple supports, and will therefore still have separate elements across the spine, even though the slips may not be separated.
Sewing supports which consist of two elements of a suitable material (e.g. tanned or alum-tawed skin, cord, etc.) lying side by side across the spine of a bookblock. They are usually sewn by taking the thread between the two elements with straight or linked sewing, but may from the seventeenth century onwards be sewn around as if they were a single sewing support (double sewing support sewn as one), which accelerated the process of sewing whilst preserving the strength of the double slips for the purposes of board attachment.
Sewing supports that are placed on the surface of the spine of a bookblock and to which the gatherings are sewn.
Sewing supports that are placed in recesses cut across the spine of a bookblock and to which the gatherings are sewn.
Sewing supports made of flat strips of material, such as parchment or textile, which will in most cases not create raised bands on the spine of a book. On very rare occasions, flat parchment supports may be split to create flat double supports.
The sewing support material is twisted. Cords, of course, will always be twisted, but skin materials were also twisted in order to give them an even, round cross section suited to sewing. It is not always possible to determine whether a core has been twisted or rolled when only a cut or broken cross section is visible, and in these cases it is safer to offer both options in the form 'twisted or rolled?'.
A wound support which has only a single element.
Pierced sewing supports which appear as separate pieces on the spine of a bookblock with spaces in between them. There will usually be two or more of them, but single separate pierced supports may occasionally be found, distinguished from continuous pierced sewing supports by covering less than half the height of the spine. Separate pierced sewing supports usually have two sewing stations for each gathering, but shorter examples with only one sewing station (for chainstitch sewing structures only) or longer ones with three or more stations have been recorded. Both longstitch and chainstitch sewing were used with separate pierced sewing supports, or combinations of both within the same support.
Pierced sewing supports which cover the entire spine of a bookblock from head to tail and side to side in one piece (though they may be laminated).