They used to be called air markers. They would have a company logo then an arrow pointing the direction to the airport and and mileage. The Shell Oil distributor in downtown Port Angeles, WA used to have a neat one on the corrugated roof of the operation that went back to the 30's. They kept painting it every few years. I remember it as a kid. Then there was some kind of county reg. about advertising on roofs. Some local pilots who liked the history of it tried to get it grandfathered in but lost the effort, and it was painted over.
Here is another slant on the air marker, pointing to the town of Port Angeles from the airport. FWIW the hangar in the photo is still out at the PA airport, but it was added on to on each side so it looks like one big building. The tower on the roof is gone.
This picture was taken by a long time local pilot and my dad made a copy of it 30+ years ago. The caption is, "Port Angeles Hangar through the struts of my cub-1937. Charles Fenwick" I have it framed in my home office.
I guess roof signs are now just advertising now. Back in the day it was to provide a service to aviation and advertise.
http://www.backcountrypilot.org/gallery ... pos=-12797