1
general::
Phrase(s): leave no stone unturned
Fig. to search in all possible places. (As if one might search under every rock.) • Don’t worry. We’ll find your stolen car. We’ll leave no stone unturned. • In searching for a nice place to live, we left no stone unturned.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Make every possible effort, use every possible source or resource. For example, To raise ten thousand dollars to keep the shelter open, we must leave no stone unturned. This expression alludes to an ancient Greek legend about a general who buried a large treasure in his tent when he was defeated in battle. Those seeking the treasure consulted the Oracle of Delphi, who advised them to move every stone. The present form dates from the mid-1500s.
American Heritage Idioms