in Indian file 成单行；成一路纵队；列成单行纵队

【例句】
Along this road the inhabitants slowly moved in Indian file.
居民们列成单行,沿着这条路缓缓行进。

The undergrowth was so thick that we had to force our way through in Indian file.
下层灌丛太密,我们只得成纵队行进。