Final answer:
Jack rafters are the type of rafters that do not extend the full distance from the top plate to the ridge board, unlike common, hip, and valley rafters.
Step-by-step explanation:
The type of rafters that never extend the full distance from the top plate to the ridge board are Jack rafters. These rafters are used in roof framing and are shorter than the main rafters.
Jack rafters are categorized into hip jack rafters, which connect to hip rafters, and valley jack rafters, which connect to valley rafters.
Neither extend the full distance to the ridge board, which is the horizontal structural member at the peak of the roof where the rafters meet.
In contrast, common rafters span from the top plate to the ridge board, hip rafters run from the corners of the building to the ridge, forming the external angle of the roof, and valley rafters form the internal angles of the roof, running from the top plate to the ridge board where two roof planes intersect.