The study of the physical structure of the book, which promotes a better understanding of its production and subsequent history. The term was initially coined in 1943 in relation to the listing of texts in catalogue form but was subsequently applied to book structures. From the late nineteenth century on, advances in the study of book structures led to the formulation of certain guidelines for reconstructing their historical development, since such structures vary with time and place. Variable features include the number of leaves used in a quire, the relative disposition of the hair and flesh sides of the parchment, the manner of pricking and ruling (and whether these processes were conducted before or after the leaves were folded, one or more leaves at a time, or with the aid of a template), and how a book was sewn and bound. The examination of a book's structure can shed considerable light on its method of construction, place of origin, and provenance and can help to reconstruct its original appearance.