What is overcasting for book binding?

Overcasting in bookbinding is a technique used to secure the edges of the signatures (groups of pages) together by stitching them with thread. This method not only reinforces the spine but also helps to prevent the pages from fraying or separating. Overcasting can be employed in both hand-bound and machine-bound books, providing durability and a neat finish. It is often used in softcover books and notebooks.