gathering

Process by which signatures are assembled together, in particular by adding endpapers.

sheet

Front and back of each sheet in a book signature.

endpaper

Sheet that is folded in half and glued inside the front and back boards to protect the first and last printed pages.

signature

Sheet that is printed and folded to make up a section of a book; it is meant to be combined with other signatures.

bone folder

Very thin blade made from bone or wood; it is used to fold and glue sheets together and to work the bookbinding leather.