In platform construction, what is the term for a vertical part of the frame that is cut less than full length?

In platform construction, the term used for a vertical part of the frame that is cut less than full length is "jack trimmer or cripple." This terminology refers specifically to smaller framing members that provide support around openings such as doors or windows. A jack trimmer, also known as a cripple, is typically used to fill the space between a header and the bottom plate of a wall or under a window header, thereby aiding in structural support while allowing for more efficient usage of materials.

The other terms mentioned do refer to different components of framing. A header is a horizontal framing member placed over doors and windows to support the load above those openings. A short stud, while it could theoretically describe a vertical framing member that does not extend the full height of a wall, isn't the most accurate term for this scenario. Blocking studs are used to provide lateral support or to fill gaps between framing members but do not specifically refer to framing around openings. Thus, the use of jack trimmer or cripple is more precise in the context of platform construction.