Antonyms for the phrase "run it up a flagpole" can be applied based on the different interpretations of the idiom. The phrase can mean 'to test a new idea or proposal,' so antonyms for this interpretation would be 'reject,' 'disapprove,' or 'discard.' Alternatively, the phrase can denote 'to promote or endorse a new idea' wherein antonyms would be 'conceal,' 'hide,' or 'suppress.' The phrase could also be understood as 'to try out something new or untested' Thus, antonyms for this approach would be 'maintain the status quo,' 'stick to the old ways,' or 'resist change.' Most importantly, it is essential to consider the context of the phrase to determine the appropriate antonyms.