Use the Cortina Safety Products Roof Warning Line Perimeter on rooftops, construction sites, in parking lots, manufacturing plants, and office buildings. This simple to assemble Roof Warning Line Perimeter, with it's easy pennant flag tie off system, is easy to set up and remove quickly, and stores easily! The warning line shall be staged and supported in such a way that it is no less than 34 inches from the walking/working surface at its lowest point and no more than 39 inches at its highest point.