What is used over door/window openings to transfer superimposed loads to vertical members?

Headers are structural elements used above door and window openings to support the load from the roof and upper floors, transferring that load to the vertical members, typically the studs on either side of the opening. This distribution of load is crucial in maintaining the structural integrity of a building.

When a door or window is cut into a wall, it creates a weak point where the load must be redirected without causing damage or potential failure. Headers are designed to handle this redistribution effectively. They are usually made of sturdy materials like lumber or engineered wood products and are sized based on the width of the opening and the load they need to carry.

The other choices do not serve this specific structural function. Ceiling joists support the ceiling and are not used directly at openings. Rafters are part of the roof structure, providing support for the roof itself. Wall top plates serve as the horizontal members at the top of the wall framing, but they do not specifically function to carry the loads over openings like headers do. Thus, headers are the correct answer for transferring loads above doors and windows.