You could use this on the roof on the slide out, but not sure if you would want to use aluminum. I would recommend Eternabond roof seal, linked below. When applying this tape you must make sure that the surface is completely clean, you may use EternaClean if you choose. This is a microsealant in a tape form, it is not a tape. It needs to aggressively be activated to create that bond for a long term hold. Using the roller makes it easier. See quick demo video below.