Imagine a castle. Now imagine it as as your Dungeon Master's Screen. This is probably about as close as you can get to putting and actual wall between you and your players.

Certain game designers and players I know would probably say this speaks volumes about the adversarial nature of the GM/Player relationship in Dungeons & Dragons. Me? I'm waiting for the DM siege weapons so I can fling dice across the table at anyone who isn't paying attention. Or maybe a pencil-firing ballista... ok, yeah, that would poke and eye out, but damn it YOU SHOULD HAVE BEEN FOCUSING ON THE GAME!