How to Use a Speed Square to Mark Angles, Rafters, Slope

How to use the speed square as a saw guide and to scribe parallel lines. How to use a speed square to find angles and for rafter layout. How to cut angles. What are the slope and the common rafter pitches? How to find all of it using the most important tool for carpentry layout. Good resources: https://www.amazon.com/shop/colfaxmath (paid link)