The bookends hold a collection of CD's vertically on a shelf the same way larger bookends are used for holding books.
Step 1: HEATING AND BENDING
If you heat them first, however, they will bend without breaking. Folding them to 90 degrees turns out to be fairly simple. Just heat the line where you want them to bend with a propane torch, being careful to not burn the plastic. When the CD becomes flexible, hold it down with a block of wood and use another block of wood to fold the exposed area up against the side of the block.
Hold it until the plastic cools and it will keep the 90 degree angle.
I torched the shiny side of the CD. Any paint on the top side of the CD might burn if it is in direct contact with the flame. In making this bookend, the paint on the other side was not scorched.
Step 2: GLUE THE CDs TOGETHER -- Method One
In order to avoid making a commercial endorsement, I forget the name of the glue I used here. It was something like Ape Glue, or Simian Glue.
Clean the surfaces first with alcohol, and dry them with a clean cotton cloth. Apply the glue and clamp the CD's together with clothes pins until the glue dries.
Step 3: "GLUE" ALTERNATIVE - Method Two
The pictures below demonstrate how well the acetone fuses the plastic together. In my test, the CD broke before the acetone joint let go. It only takes a drop or two of this solvent to do the job. Clamp the parts together with clothespins for a few minutes and you are ready to go.