Roof Oddity

Is the gap you are referring to about half an inch wide, kinda U shaped and runs the length of the roof on both sides? If it is, no worries, that's the rain gutter. If it's not, could you post a pic so we would know what we're dealing with? The gaps I am familiar with are in the rear pillar about halfway down the rear window and run horizontal. There is another one in the front windshield pillar about 3" down from the top.