What is the name of the wood framing member that supports a header over a door?

The correct choice is the trimmer. In wood framing, a trimmer is a framing member that supports the header above a door or window opening. It is typically positioned vertically and connects the bottom of the header to the floor plate or sole plate, providing necessary structural support. The trimmer helps to transfer the load from the header down to the framing below, ensuring stability and strength in the structural integrity of the wall.

While the header is the horizontal member that spans the opening above a door, it is the trimmer that specifically handles the load-bearing function in this context. Jacks, also known as jack studs, are shorter members that extend from the bottom plate to support the header, but they do not directly support the header in the same way the trimmer does. King studs, on the other hand, are the full-length studs that run from the bottom plate to the top plate and flank the opening, providing additional support but do not specifically serve as the member that supports the header. Understanding the distinct roles of these components is essential in framing practices.