Johnson Level & Tool Mfg. RAS-1 - Manual (Page 6)

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TYPES OF RAFTERS
COMMON RAFTER: A rafter that runs perpendicular (90°)
from the wall plate to the roof ridge when looking straight
down at the roof. When looking from the side, its length
forms the diagonal leg (or hypotenuse) of a right triangle
that has its vertical leg equal to the rise and its horizontal leg
equal to the run (see Figures 1, 3 and 8).
VALLEY RAFTER: A rafter that runs from the wall plate to
the roof ridge at the intersection of the gable extension with
the main roof (see Figures 1, 8, 12 and 13).
VALLEY JACK RAFTER: A rafter that runs from a valley rafter
to the roof ridge, 90° from the roof ridge (see Figures 1, 8
and 15).
HIP RAFTER: A rafter that runs diagonally from the top of
the wall plate to the roof ridge, so as to form an outside
corner of the roof (see Figures 1, 8, 9 and 10).
HIP JACK RAFTER: A rafter that runs from the top of the
wall plate to a hip rafter at 90° to the wall plate (see Figures
1, 8 and 14).
CRIPPLE JACK RAFTER: A rafter that runs from a hip rafter
to a valley rafter, perpendicular to the roof ridge (see Figures
1 and 8).
DORMER RAFTER: A rafter which sets on top of the main
roof without cutting into it, thus causing the main roof not to
weaken. For example, when remodeling or when solar panels
are added (see Figure 1).