The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
Square app will allow one to measure roof area for square footage. Best results are to do point to point squares take the length and width of each side and multiply on calculator this will give you square footage. IE. 10ft x 10 ft =100 sq ft, and in roofing terms that's 1 square.