Final answer:
The correct term for the short lengths of 2x material used above door and window openings is 'headers', which distribute the load to the vertical studs beside the openings.
Step-by-step explanation:
The short lengths of 2x material used above door openings and above and under window openings are called headers. In building construction, these headers are horizontal structural members used to distribute loads they carry above to vertical studs on either side of an opening, such as a door or window. The function of a lintel is similar, but it is usually a crossbeam used in stone or masonry structures, supporting the weight above a doorway. Meanwhile, sills are the horizontal pieces found at the bottom of windows, and sashes are the moving parts of the window that contain the glass.
The short lengths of 2x material used above door openings and above and under window openings are called lintels. Lintels are a type of crossbeam that provide structural support for the masonry above them. They are typically made of stone or wood and help distribute the weight of the wall or roof above the opening.