This is something that is pretty common where I live, in Bavaria, but I cannot speak to how wide-spread this technique actually is.
The gist of it is this: you take a board, cut it up along its length using a repeating pattern, and end up with two identical pieces of trim that you can layer to create any number of trim effects for a roof or virutally any other woodworking project.
Around here, these are mainly made from wood, but as long as you have a saw capable of cutting the pattern you need you can use any material you want, like sheet metal or plastic, and even leather or fabric.
Check out the video to see how easy it is to do, and how you can easily make your own patterns - or just keep reading!
Step 1: What It Can Look Like
Here are some examples of the many different looks you can achieve with some basic patterns. By simply moving one piece sideways, the resulting pattern can change drastically, and you can chose to paint one board in a different color to further highlight.
You can also download the templates for the patterns shown in order to use them yourself.
Step 2: How to Create Your Own Patterns
To make a full pattern, first draw half a pattern that should start at the center on one side of your working area and ends in the center. You should keep to one half of it, although you can experiment with breaking the middle line.
Now rotate that half-pattern by 180° with the middle of your working area as the center of the rotation. The image above really explains it a lot better than I can.
The important part is that the pattern needs to start and end at the center of each side so you can repeat it for as long as you need - or as long as your board allows.
If you do create your own patterns, please share them with me!