The American Staffy and Pit Bull Terrier are inherently linked. The American Staffy is recognised as a show animal and the Pit Bull is not. They were once the same breed until after dog fighting was made illegal in the United States and breeders of the American Staffy aimed to breed out the Staffy's aggressive nature.
There is absolutely no evidence for the existence of any kind of “locking mechanism” unique to the structure of the jaw and/or teeth of the American Pit Bull Terrier.” Staffies and bully breeds don't have locking jaws. No animal does.