On "Ask This Old House" today, I really enjoyed learning about solar attic fans and the installation process. I would like to install one of these in my home. The instructions and demo were great regarding the actual install. I am confident I can do this now. I further understand the importance of roof safety and for the temporary "ledge" and strap. What was not illustrated enough however, for me and I believe may be for others, was how the both the temporary safety ledge and strap(s) were fastened to the roof and how any holes made by those nails, screws, and/or clamps for these safety features were fixed and or sealed at the completion of the project. I learned a long time ago from my Dad, any time you go on a roof you impose a certain amount of stress and damage to the shingles and may invite paths for water damage. Could you help me here regarding this very important part of the install and un-install?