So the light is mounted on the wall so the wider part faces up?? and the wider part is open whereas the narrow part has glass at the top. Looking at the mounting hardware, it would not be a good idea to reverse the direction of the light so the open wider part is at the bottom?

If you notice the mounting plate, you'll see the mounting bolts that go into the wall will fall into the skinnier part of the hole, which would secure it much better.

You could mount it in the opposite direction if you're able to secure it into place, but it is not designed to be reversible.