Make a Square Cut Mark
Make a mark at the location you want to cut off on your board.
Lay the framing triangle on top of the board and push the square lip against the side of the board.
Slide the triangle along the board until the top edge is lined up with the mark you made.
Set your pencil point on the mark that you made and slide it along the straightedge of the triangle giving you a square cut edge.
Make an Angle Cut Mark
Set the triangle flatly on top of the board you want to cut with the lip end being on the side you want to start your angle from.
Push the pivot edge against the point you are starting your angle at. The pivot edge says "pivot" and there is an arrow pointing at it.
Pull the other edge of the lip away from the side of the board until the angle mark lines up with the edge of the board. Make sure to keep the pivot end firmly pressed at the point the entire time you are adjusting the other end.
Make a mark along the short edge of the square that has inch measurements along it.
Use a straightedge to extend the mark along the board.
Cut Rafter Ends
Push the lip against the side of the rafter you want to cut with the pivot point at the mark your angle will start at.
Use the common markings on your framing triangle to create your rafter angle. The markings correspond to the pitch of the roof.
Tip the other end of the lip away from the rafter until the correct common mark is on the edge of the wood.
Use the Hip-Val markings for the ends of the rafters that are going in to a hip or a valley.