A book, when opened, should lie flat when placed on a table, and stay that way without help from its reader’s hands. It should open to its fullest extent, so that the whole of the page, or pair of pages, can be used: for photographs that might run into or across the central margins, for side-notes or other text that needs to occupy an inner margin. One might remark also that a book open on a table – while the reader holds a cup of tea in both hands (for warmth and comfort), or sews a button on a shirt, or carries a young child – is no more than a mark of decent civilization. So the binding should be strong enough to withstand this opening-out. The spine will of course begin to show signs of wear with this opening – that is in the nature of the materials – but it should not split, and the pages should not fall out.