Keeps your loose cable ends from falling down behind the desk, saving you from having to fish them back out with a coat hanger or enlist your kid and his small hands to grab them.
You may want to scale it up a tad if you intend to use the holes with #6 screws; right now, they'll take finishing nails.
Feel free to modify and repost.
2a) Nail to desk
2b) Cut off flanges on end and use double-sided foam tape to stick it down.
3) Stick your cables in it.