It is a Swedish Flat bread and is different from other Flat Breads in that it uses some Rye four, lots of melted butter and maple syrup, as well as yeast. To prevent it from rising up and forming a ball shape like for Pita Bread, they use a corrugated rolling pin, and to prevent black char both sides are brushed with a stiff brush to remove loose flour. I don’t have a corrugated rolling pin, so I go over the whole thing with an old meat tenderizer hammer, which creates the same pattern. Here is a YouTube Video showing one going into a wood fired oven. https://www.youtube.com/watch?v=U8fz_W9fGYg
As I write this, I am recovering from my mid-day siesta while drinking a strong cup coffee, and munching on a quarter of a Swedish Thin Bread (Tunnbröd).