Which component do jack rafters connect to at the lower end?

Jack rafters are an essential component of a roof framing system, specifically used in conjunction with hip or valley rafters. They serve the purpose of connecting the roof at a lower elevation while providing structural support and maintaining the roof's slope. At the lower end, jack rafters connect to the wall plate, which is a horizontal member that sits on top of the wall studs and provides a stable base for the rafters. This connection allows for effective load distribution and ensures the overall stability of the roof structure.

The wall plate plays a crucial role in anchoring the jack rafters and enabling the proper transfer of loads from the roof down to the walls below. In contrast, the other components listed—top plate, joist, and ridge board—serve different functions in the overall structural system. The top plate is located at the top of the wall studs and does not provide the necessary anchoring for jack rafters. Joists are horizontal structural members that support floors, not roofs. The ridge board is found at the peak of the roof and serves to align and support the upper ends of the rafters, but it does not connect with jack rafters at the lower end. Therefore, the correct connection point for jack rafters is indeed the wall plate