I attached two small lengths of scrap wood to the back with screws that were long enough to penetrate the reclaimed wood, but not too long to go all the way through.
But back to my wire rack! I gave it a quick makeover with some farmhouse/industrial spray paint- something dark and metallic to stand out against my reclaimed wood.
While the paint dried, I installed a hanging wire on the back of the wooden backing I had made earlier.
And then I attached the shelf to the wood! ( Find out how I did it HERE! ) . It will live in my home office and help me keep my desk clear of clutter.