An upper decker. That's when you take a crap on the tank of the toilet rather than the bowl. I would like to to do this at a bar on 6th St in austin preferably. I have also wanted to try getting a blumpkin from a lady while doing an upper decker. Originally Posted by Buddys PlaceWhy do you have to go to a bar on 6th Street? Why not take a shit on (or in?) the toilet tank in your own home?