From Longman Dictionary of Contemporary Englishsingle fileˌsingle ˈfile noun → in single file —single file adverb
Examples from the Corpus
single file• Ambush patrols at night were always in single file, with no point or flank security.• A narrow spiral staircase leads up from chamber 2b to 2c; characters must ascend in single file.• Teams of horses in single file hauled trains of a dozen flat-topped wagons loaded with granite along these rails.• The stairs are approached along a raised pavement so narrow the people must have walked along it in single file.• Men passed us, dark, bearded, stern, armed with sticks, walking swiftly in single file.• Okay single file, we're coming to a wood.• Then we are instructed to leave Damrosch Park single file.• The jungle area we had to go into was so thick, the APCs could only travel single file. 