Block of wood
Squirrels enjoy soft woods, and placing another piece of wood near by won't necessarily deter them from chewing on your furniture. I suggest using repellents or exclusion methods for control. Some chemicals such as Capsaicin "which is made from hot red peppers" can keep them from chewing on your furniture. If the chemical deterrents don't work then I would recommended covering the furniture with metal or hardware cloth when not in use, and finally if all else fails, removal of the animals via trapping. Most states require a trapping licences, so I would recommend either contacting a licensed professional or your state Natural Resources Division for more information on trapping.