At first I didn't want to use any module other than the main one, hoping that the unit itself would be versatile enough to accommodate every condition. I have realized that sometimes, 'specials' are necessary- the exceptions that make the system work. In my case, in order to finish an edge properly, I need some half modules. These were made simply by slicing the brick before drying.
The shape, I've realized, is interesting because it has the exact same profile on four of its sides.