Which component is not part of a flat roof overhang installation?

In the context of flat roof overhang installations, the component that is not typically included is the soffit air vent. Soffit air vents are utilized primarily for ventilation in attic spaces and are more relevant to sloped roofs where airflow is needed to regulate temperature and moisture in the attic area.

Flat roof overhangs instead focus on ensuring proper drainage and protecting the building from water intrusion. A metal gravel stop is designed to help direct water away from the roof edge, while built-up roofing provides a waterproof layer suitable for flat roofs. Additionally, an exterior plywood soffit is often used as part of the aesthetic and structural elements of the overhang itself. Thus, the soffit air vent doesn't play a significant role in the context of flat roof overhangs, making it the correct choice for this question.