Run both boards long and cut in place.
Roof return framing.
This structure supports all roof sheathing materials such as plywood sheathing underlayment and of course shingles.
The run or half the building span is the base of the triangle.
Notches under the rafters allow the ledger stock to be full dimension on the ends to better support the return framing.
The rise or height of the roof at its peak is the altitude of the triangle.
Whether you are framing a cornice return capped with a hip roof or a shed roof the first step is to install the subfascia and the ledger.
Return eaves a common roof structure is made of trusses or rafters.
And the line length measurement from the roof peak to the building wall is the hypotenuse.