Trim marks are the lines at the edge of a printed page that show where the page should be cut. They are also called crop marks or printer’s marks. Trim marks should not be confused with registration marks, which are used to align the paper during printing.
Trim marks are printed on a book’s spine and on its fore-edge (the top, bottom, and outside edges of the pages). They indicate where the pages should be trimmed during the binding process.
The spine trim mark shows where the pages should be trimmed so that the text block is flush with the spine of the book cover. The fore edge trim marks show where the pages should be trimmed so that the text block is flush with the fore edge of the book cover (the top, bottom, and outside edges of the pages).
Trim marks indicate the finished size of the page after trimming. The width of the trim marks should be equal to the amount that will be trimmed off the page. For example, if a page will be trimmed down to 8.5″ x 11″, the trim marks should be 0.25″ from each edge.
Most books are trimmed using a guillotine cutter, which cuts all the pages at once. The pages are usually trimmed a little bit larger than the finished size, and then the book is rebound. This allows for a small amount of variation in the trimming process, so that the finished book will be the correct size.
Some books are trimmed using a laser cutter, which can cut each page individually. This is often done for very large books, or for books with complex trimming requirements.
Trim marks are very important when it comes to books. They help ensure that the pages are all the same size and that the book looks uniform when it is finished. Without trim marks, it would be very difficult to produce a professional-looking book.