https://swaay.com/u/gordonperkins33101/about/">https://swaay.com/u/gordonperkins33101/about/. A high quality roofing will have them set up around the side of the roofline, where vertical walls meet the roofing system https://haimaetkm877789.tkzblog.com/39300659/stay-dry-roofing-fundamentals-explained