I always do it under the table; something I instinctively do without ever being told to. Now I wonder if I might have picked up on nonverbal cues at some point in the past. If I were someplace where chopsticks were the norm, I would probably just carry my own as I find the disposable wooden ones very off putting. I have to wonder if there is a rule about using your own chopsticks though.

I don't often bring sandpaper or dremel tools to a restaurant.