The chain was attached at the fore-edge of a book rather than to its spine.
From the en.wikipedia.org
I ran my thumb along its fore edge, narrow and sharp against my skin.
From the guardian.co.uk
Some artist's books go even further, by using fore-edge painting.
From the en.wikipedia.org
Titles were also commonly written onto the fore-edge.
From the en.wikipedia.org
They were riveted to the fore-edge of the front covers and many of them have been pulled away and lost.
From the en.wikipedia.org
University tour guides often remark on the resemblance between each of the elements of the building's facade and the fore edge of a book.
From the en.wikipedia.org
The band of leather, vellum or parchment which closed the book was often used for the inscription of the title, which was thus on the fore-edge instead of on the spine.
From the en.wikipedia.org
The book is then carried forward to the trimming station, where a three-knife trimmer will simultaneously cut the top and bottom and the fore-edge of the paperback to leave clear square edges.
From the en.wikipedia.org
The mainsail is triangular, rigged fore-and-aft with the lead edge fixed to the mast.