Twist-resistant rivet nuts install through mounting surfaces and create a female-threaded mounting point. They feature flat faces, similar to a hex nut, that wedge against the mounting surface and resist rotation. They are commonly used for high-torque applications that would cause regular rivet nuts to spin in place.
https://www.grainger.com/product/Rivet-Nut-5-16-18-Thread-Size-5NNN4?searchQuery=5NNN4&searchBar=true