Situation: I am pushing the bookshelf with another bookshelf in my ten o'clock direction and the window behind me.
Alternative situations: I am trying to find a specific kind of book so the numbers on the side of the bookshelf to guide myself. Having left my backpack on a table in my 8 o'clock direction, I am wiping the books in front of me.
Question: Which way should I turn to grab my backpack behind me?