Labeling of binders

I am in the middle of a labeling project. We are setting up an indexing system (similar to a library) for our parts manuals, catalogs, etc. I am printing up the index number labels for the binders, but I was wondering, is there a correct way to rotate the label? I've heard that the "top of the text" should be towards the left (as you are looking at it), but that would end up reading from the bottom up. Is this correct, or should the top of the text be to the right so that you are reading from the top down? Thank you for your response.