Look UP--vanishing point for the vertical lines pops UP.
Look DOWN--vanishing point for the vertical lines pops DOWN.
And finding the center helps you draw the tilting verticals more accurately.
I particularly love this piece by Steve, it is really one of my all-time-favorite sketches. He takes something mundane that we all have walked by thousands of times and never noticed, and elevates it to the status of art by drawing our attention to its detail and shapes. So beautifully drawn and full of character. Such a great sketch!