Here are some instructions on how to make a simple origami (paper folding) bookmark:
Take a square of paper. It can be patterned origami paper, gift paper or even office paper, just as long as it’s easy to fold. The square should not be much bigger than 10 cm/4 inches across, unless you intend to use the mark for a big book. The images show what the paper should look like after you follow each step of the instructions. The two sides of the paper are shown in different colours to make things easier, and the edges and fold lines are shown as black lines.
Fold the paper in half diagonally (corner to corner), and then unfold. Repeat with the other two corners. This is to find the middle and to make the rest of the folding easier. If the paper is thick or stiff it can help to reverse the folds.
Fold three of the corners in so that they meet in the middle. You now have a piece of paper resembling an open envelope. For the next two steps, ignore the flap.
Fold the square diagonally in two. You now have a folded triangle with a triangular flap coming out of it.
Fold the triangle in half again across the middle. You now have a smaller folded triangle with a flap.
Look at the end the flap is on. You will see two pockets inside the triangle. Tuck the flap into the one farther away and slide it in all the way. Crease to secure.
You now have a book-corner protector or a corner bookmark. Just slide onto the corners of pages. The bookmark is thick and a bit heavy, and will hold better if you stick the corners of several pages into it rather than just one.
Apologies if the design is copyrighted - I was taught it by a friend and have no idea where she learned it.