And nowadays they are supplemented and partially superseded by European EN directives. This is the kind of stuff that hardly anyone realizes but is enormously helpful in everyday life. Your toilet seat breaks, you just go ahead and buy a new one. Its mount points, dimensions, and load bearing characteristics are standardized so no need to get a degree in toiletology or whatever. Just buy any one you like. Same idea with light bulbs, printer paper, piping connections, door jambs, etc. etc. Standardization makes life SO much easier.