- Cut the cardboard to go down the spine: Cut a strip of light card. It should be about half the height of the book, and just wide enough to slip down the spine when the book is open. 1cm worked for this Moleskine journal. If in doubt, cut it a little bit too wide, then trim it down until it fits.
- Cut the bookmark ribbon: Use a ribbon that is narrower than the thickness of the closed book. Cut a piece that is at least 6cm longer than the book (A bit over 2 inches). I like to keep the ribbon long, then trim it to length when I’m finished (cut it at an angle, to stop fraying). You can also use more than one ribbon, if you want lots of bookmarks.
- Attach the ribbon to the card: Attach your ribbon(s) to the top of the strip of card. Overlap the ends, rather than matching them up (see the photos above) – basically, the ribbon should come off the card like a whip off a handle. Staple ribbon and card together, then wrap the join with masking or duct tape for durability.
- Attach bookmark to book: Open the book flat, then slide the strip of card all the way into the hollow spine, leaving the ribbon hanging out. When the book is closed, it should hold the card snugly in place.
- Reusing the bookmark: The bookmark should pull out easily when you want to add it to a new journal.
(Edited for clarity)
(Edited again to add: This also works with multiple ribbons. My current version has four.)