What is the name of the bottom horizontal member in frame and platform construction?

The bottom horizontal member in frame and platform construction is known as the soleplate. It serves as the base for vertical framing members, typically called studs, and provides stability and support to the entire wall structure. The soleplate is essential for anchoring the studs to the floor and ensuring proper alignment during construction. This component also plays a role in distributing loads from the wall above down to the foundation, which is crucial for the overall integrity of the building.

In contrast, a header is used in framing to support the weight of the structure above openings like doors and windows. Studs are the vertical members that form the walls, while cripples are short framing members situated above or below a header that support the wall above openings. All these components have their specific roles in framing; however, when identifying the specific function of the bottom horizontal member, the term soleplate is the accurate choice.