Roof cover ads, ours included, almost always show the same thing: a long, flat, empty roof. A real North American trailer has a rooftop air conditioner, a few vent covers and a plumbing vent, and the owner who looks at that smooth roof in the photo, then at their own, concludes the cover was made for someone else. So the roof stays bare, and rain lingers around the skylights and seams that a cover is supposed to keep dry. Here’s what we can tell you, and only that. The cover is a flat sheet of waterproof fabric, 10 ft wide, in eight lengths up to 41 ft. It covers everything on the roof, and the straps hook under the edge of the body on all four sides. Over an air conditioner, it goes on the same way: it runs over the unit, the vent covers and the vents, then the straps pull it tight. With a rooftop air conditioner, take the next length up, because the unit uses up a bit of cover. An antenna gets laid down or removed before installation. And you have 14 days: put it on, see how it sits over your air conditioner, and if it doesn’t work, it goes back.