Trim marks, sometimes known as crop marks or printer’s marks, indicate where pages should be cut out of a printed book. Registration marks (sometimes called registration lines) should be distinct from trim marks because their purpose is different – registration marks align paper during printing. In contrast, trim marks show where to cut.
Trim marks are printed on both the spine and fore-edge of books to indicate where pages should be cut during binding. They show where pages need to be trimmed when it is time for trimming.
The spine trim mark indicates where pages should be trimmed to ensure that their text block sits flush with the spine of a book cover, and fore-edge trim marks demonstrate where pages need to be trimmed to ensure their text blocks sit flush against its fore-edge (the top, bottom, and outside edges of pages).
Trim marks indicate the final dimensions of a page after being cut down to size, such as when trimming to an 8.5″x 11″. Their width should reflect how much will be removed; for instance, if cutting will reduce it to an 8.5″ x 11″, trim marks should be placed 0.25″ from either edge of the page.
Most books are trimmed using a guillotine cutter, which cuts all pages simultaneously. Pages are typically cut slightly larger than their finished size before rebounding the book to account for slight variations during trimming – this ensures that it will be the desired size when finished.
Some books may be trimmed with a laser cutter, which can individually cut each page. This process is often utilized when dealing with very large books or those requiring complex trimming requirements.
Trim marks are integral components of book production. They ensure that pages are of equal sizes and make for an aesthetically pleasing end product, without which producing professional-looking books would be much harder.