Back in my day the arrogant devs just used printer paper and a hand drawn sign saying "GO AWAY!" taped to the back of their chair.
replies(2):
I went so far as to put a post-it note saying "I'M BUSY" on my headphones. The usual suspect came up to me and tapped me on the shoulder until I reacted, all so he could tell me, "hah, someone put a post-it note on your headphones!"
If I didn't kill someone that day, it's unlikely that I ever would.