Sometimes you have an unused space in your Eurorack case that has no module. It's customary to cover these spaces with a blank panel so that dust, dirt, small animals, or woodchips don't get into the case. Plus, it looks cool. These blank panels have been designed to look nice and function well. The city of Grosse Pointe, Michigan is featured in this panel design with it's topographical elevation contour lines in silver on a white background (that's Lake St. Clair at the very bottom-right).