Final answer:
Hip rafters are the structural elements that extend diagonally from the top plate corners to the ridge board, providing support for the corners of a hip roof.
Step-by-step explanation:
The type of rafters that extend diagonally from the corners formed by the top plates to the ridge board are known as hip rafters. These rafters perform a crucial structural function in various types of roof construction.
They provide the necessary support for the corners of a roof and are typically found in structures with a hip roof design, where all sides slope downwards to the walls, creating a more complex framework than a simple gabled roof.