The headband and tailband (collectively, endbands) are the decorative stitched elements at the top and bottom of the spine. In traditional stitched structures, the endbands were stitched on to the text block itself and helped to reinforce the binding—particularly when the book was pulled from the shelf by its head, as is so common. Sometimes the endbands were stitched round a core of rolled vellum or a strip of leather. The more decorative ones were made from coloured silk. But most endbands on modern books are cut from a pre-made roll and stuck on before the book is covered. This type of endband is not strengthening at all and also not nearly as romantic.
The headcap and tailcap refer to the sections of the spine covering that sit above the endbands and are tucked in behind them. The caps and the bands reinforce each other. I’ve only recently discovered that bookbinders and book conservators also call the caps ears! This is way cool. Now, do you like being pulled along by your ear? I don’t think so. So next time you go to pull a book off your shelves, spare a thought for the poor old headband and headcap—if, indeed, they are still present. If you can, push the books either side of the one you want in, so you can pull out your book by the whole spine and leave its poor ears alone.