Cocked Spine
A condition defect in which the spine of a book is tilted or slanting at an angle rather than running straight and square — usually caused by improper storage or shelving.
In context
The cocked spine told her it had been shelved too loosely and leaned for years — correctable if caught early, permanent if not.
He described it honestly in the listing: 'slight cocking to spine, else near fine.'
Even a minor cock to the spine will drop a book a full condition grade for most serious collectors.
A cocked spine is what happens when a book spends too long leaning. On an underfull shelf, without adequate support from its neighbors or from bookends, a book gradually tilts under its own weight. The text block, the binding, and the cover boards all shift slightly in the same direction until the spine — which should be perfectly vertical — runs at a visible angle from head to tail. View the book from above and it looks square; view it straight on and the whole thing leans like a tired person at the end of a long day.
The cocking develops slowly enough that it's often not noticed until it's already established. A book that has leaned for months may not look dramatically wrong, but a bookseller comparing it to a square copy will see the angle immediately. Once cocking has set — once the binding has taken on the slant — it is difficult to reverse without risking further damage. Early, mild cocking can sometimes be corrected by shelving the book very firmly upright between well-supported neighbors and giving the binding months to re-set, but this works imperfectly and not always. Significant cocking is generally considered a permanent defect.
Prevention is straightforward: books need support. A shelf that's too loosely packed is as damaging as one that's overfull. Good bookends — the kind that grip the shelf rather than simply pressing against the last book — make a significant difference. Books stored lying flat (stacked horizontally) don't develop cocked spines, which is why oversized art books and coffee table books, which are too large to stand upright safely, are typically stored on their sides. For standard-size books standing upright, the key is ensuring they stand rather than lean.
For collectors, a cocked spine is a condition note that appears in listings alongside foxing, shelf wear, and bumped corners — it's specific enough to be useful as a warning, common enough that experienced buyers know what to expect. The standard phrasing is "spine slightly cocked" or "moderate cocking to spine," indicating whether the tilt is barely perceptible or obvious at a glance. "Spine square" in a listing is a positive note — it means this potential problem is absent. For readers who don't buy for investment, a cocked spine is cosmetic: the text is the same, the reading experience unchanged. But it's a good reason to pay more attention to how your books are supported.