Use a ruler and pencil to draw lines on your cardboard 1 ½-inches to 3-inches apart. If your cardboard is longer than six inches draw a line at six inches to mark the length of your bookmark.
Place the cardboard on a surface that will not be damaged by a knife such as a cutting board a piece of thick cardboard or a pad of newspaper. Use a craft knife to cut along the lines you’ve marked.
Decorate and leave as is or cover with clear contact paper to protect your design.
Optional: punch a hole in the top of the bookmark and attach a tassel, a charm or a button on a length of several strands of embroidery floss or thin ribbon.