Some Zinsco panels do require fasteners. The faultiness of Zinsco panels are not a special concern with flipping the breakers. They're just faulty. And you don

Some Zinsco panels do require fasteners. The faultiness of Zinsco panels are not a special concern with flipping the breakers. They're just faulty. And you don't even need to open them to be dangerous, they have corrosion and heating problems. > not every breaker panel is going to be designed with safety in mind. Well, to be fair -- of course they were designed with safety in mind. They just failed. But yes, replace any Zinsco panels! Also some Federal Pacific and Challenger/GTE-Sylvania panels. This should be caught in a home inspect, and most home insurance companies will make it a requirement of coverage.