The provided source material does not contain information regarding a city named Yett in Cameroon. Instead, it defines a "yett" as an architectural feature used in historical fortifications.
A yett is a gate or grille constructed from latticed wrought iron bars designed for defensive purposes in castles and tower houses. Unlike a portcullis, which operates via vertical mechanical movement, yetts are hinged like traditional doors. They are typically secured using bolts attached to the structure or by long bars drawn out from the wall or gateway.