We bought plastic rain gutters from Home Depot. They offered to cut them into pieces for us...we said no. Do NOT say no...unless to have a handy hubby and a sharp saw!!
Anyway, we sawed them into four pieces. I originally planned for three feet...so glad I went with four.
Then we screwed them into the wall. We did four screws across for good measure. Just plain old screws, didn't use a fancy anchor or anything.
This is our finished project...filled with books of all sizes (some quite heavy!!) And I must say, my two year pulls on it pretty hard, and it has yet to fall or snap.
Total cost...$6.00!!