There are a handful of ironclad rules to obey (see two below), but if you follow just one, let it be this: Don't put it in the dishwasher. (bonappetit.com)
It is a near ironclad rule in the world of news management that only bad news gets released in the late afternoon on a Friday — and a summer Friday, no less! (nystateofpolitics.com)
If there is one ironclad rule about marketing, it is that you had better be practicing internally what you are preaching to the world. (treehugger.com)