In "My Life Had Stood - A Loaded Gun—" by Emily Dickinson, the poet describes using “frowning men”—likely critics with a narrow mindset—to load her figurative gun. This gun can then become an effective weapon and a powerful voice: it will go off at the poet’s command and hit its target (“when it came,” “it aimed and fired”, and “a thousand men fell down”).
So Dickinson would “use” those disapproving faces to arm herself and fight against their prejudices and limitations through literature and poetry.