Your last two are better than your first two, actually. (The Rock of Gibraltar is the logo for Prudential Securities ["The Rock"], and a line of pick-up trucks has used Bob Seeger's "Like A Rock" for ages as an ad jingle. Because rocks are tough.)
To American ears, for whatever reason, “As safe as” sounds more natural than “safe as.”
“That’s money in the bank,” is one standard “secure” idiom, meaning “a sure thing.”
“Houses” and “milk” aren’t safe. Fortresses are. So are vaults. And tanks. Rocks and mountains are safe, too, mostly.
Some things that are stereotypically certain:
If you wash your car, it will rain.
Likewise watering your yard.
"As sure as shit" is, unfortunately, the first actual simile that comes to mind. (So there's a security in misfortune.)
It's followed by the rhetorical questions, "Does a bear shit in the woods?" and "Is the pope Catholic?" Probably not what you need.
I think there's something to be said for "as sure as the sun will rise" and "as sure as the tides will change," but maybe that's just me. |
