What is a 2x4 piece supporting the header called?

A 2x4 piece that supports the header is referred to as a trimmer. The trimmer, also known as a trimmer stud, is used in framing to support the ends of the header, which spans across openings like doors and windows. Its primary function is to distribute the weight from the header to the floor or foundation. Trimmers help to create a sturdy and stable opening in the frame of a building, ensuring the structure remains sound.

In contrast, other terms have specific meanings in the context of construction. A brace typically refers to a diagonal support used to reinforce and stabilize a structure, while a king stud is a full-length stud that runs from the bottom plate to the top plate, flanking the sides of an opening and providing additional strength. Rafter, on the other hand, is a structural component that supports the roof, extending from the ridge or peak to the wall plate. Understanding these terms is crucial for effective communication and execution within the construction field.