There are two types of cover which may typically be found on a book, primary and secondary. The primary cover is the material that constitutes the immediate covering of the completed binding, but not including additional, secondary, covers such as chemises or decorated paper over a plain primary cover. For inboard bindings, the primary covering material is used to cover the boards and spine, either completely, as in full bindings, or partially, as in half and quarter bindings. In all case bindings, and bindings with external sewing supports and longstitch bindings, the case itself may also be the covering material, and thus serve a dual function as both primary covering (which therefore may be given a secondary, decorated cover) and structural component. A secondary cover can be added in addition to a primary cover (but cannot be a secondary cover unless there is a primary cover already in place), either as protection or further embellishment of the book. In the latter case they are often made from decorated materials (most often textile or paper), but purely protective secondary covers can be made made from plain materials such as tanned or alum-tawed skins or paper, or recycled paper or parchment. They may be contemporary with and part of a complete binding, or may have been added afterwards (sometimes many years afterwards) to suit the taste and needs of a later owner. Many bindings with primary covers in parchment also have a lining of white paper under the parchment, int
et bokbind kan ha to typer overtrekk, det primære overtrekket befinner seg nærmest bokblokken, mens det sekundære er trukket utenpå det primære
covers
overtrekk