Rating: 
Our cats had been scratching our couch all their lives (over 12 years)! We tried so many different cat scratching posts with toys, food, catnip. Nothing worked!
Finally we needed a new couch. So I looked up lots more ideas on the internet. All right- double-sided tape, aluminium foil, non-scratching spray,... And corrugated cardboard!
We got the new couch, put the scratching board next to it where they usually scratch on the couch. One of the cats went straight to the board and started scratching!! The other one was curious at what she was scratching but couldn't work it out. Finally I put some of the catnip on it, and now she's scratching on it too!
They haven't even thought about scratching the couch, but love the box!
I'm amazed!