Which component provides structural support at the end of floor joists and around openings?

The rim board is crucial in providing structural support at the ends of floor joists and around openings. It serves as a structural member that connects the ends of the joists to create a boundary for the floor system, ensuring stability and integrity. It also acts as a backing for fasteners used in various applications, which is essential when framing walls.

Additionally, the rim board helps in transferring loads and forces from the floor and walls above, which is vital for maintaining the overall strength of the structure. Its placement around openings, such as doorways and windows, is especially important as it helps distribute the loads to the surrounding framing, preventing structural failure.

This function differentiates the rim board from other components like headers, trimmers, or king studs, which have specific roles in framing but do not serve the same boundary and load-distribution functions as the rim board does.