Add arrow to retaining walls to indicate direction it's facing in

I just got far enough into my first game to need to place down my first retaining walls.
I found it incredibly hard, if not nearly impossible, to determine which side was sloped and which was straight. A simple arrow that indicates the direction of force or something would be greatly appreciated.

Two sides are sloped. And it is difficult for me to see this as well with the current Ghost view of the walls. The Ghosting of objects needs some work to make it easier to see things during placement, before they are built.