How many of us, as schoolchildren, were warned never to use a pencil as a bookmark, because we would "break the back of the book"? That is one of the bad things that can happen to spines and joints, but it's not the only thing.

For one more spine problem not covered on this page, please take a look at my blog post: Spine perished, a summer project.

Shelf cocked or spine slanted.

A shelf cocked book is one that cannot stand perpendicular to the shelf. It leans. In fact, the condition is also called spine lean. It may not be apparent in the photograph at left, but the book was not merely tipped for purposes of the picture. The book shown actually cannot stand straight unless closely propped on both sides.

Spine cocked books.

A spine cocked book is one in which the front and back boards do not line up. When the text block is viewed from the top or bottom, the spine- and foredge-sides are slanted, rather than square. Both hardbacks and paperbacks can become spine cocked. The picture at left shows, from top to bottom, a spine cocked hard cover, a spine cocked trade paperback, and an undamaged hard cover.

Spine cracked book.

A book with its spine cracked is one where the book automatically falls open to a place where the binding has been substantially weakened. Often, the mull or backing can be seen through the "crack" when the book lies open.

Book with split spine.

A spine split is a spine crack carried to an extreme. The book shown at left is almost completely separated along the spine, being held together by only a thread or two.

Cracked or starting hinge.

A hinge is the place on the interior of the book where the cover meets the spine. Like spines, hinges are subject to separation. A cracked hinge, sometimes also called a starting hinge, is one where the paper has started to split but the cover is still attached to the book. If the cover were actually detatched from the text block, it would be called a broken or split hinge. If the cover were completely separated from both the spine and the text block, it would be called detatched.