The protective sheet of paper glued to the inside front and back covers of a bound book, connecting the cover to the first and last pages of the text block.
From 'end' and 'sheet' (from Old English 'scēte'), bookbinding terminology that emerged during the development of durable book-binding methods in the medieval period.
Endsheets are the unsung heroes of books—they're purely structural, but centuries of bookbinders learned that without them, your book falls apart within years, so they became standard in every quality bound book.
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