the other day i told someone at work to "check [their] six" because i was pulling a heavy skid right behind them and couldn't easily stop
later they asked me if i play call of duty
no, that's just an actual thing people say
@monorail We're familiar with the clock-to-direction analogy, but we've never heard it with that specific phrasing before.
@Rosemary "check directly behind you"
imagine an analog clock with the direction you're facing being 12. "check your six" means "look towards the six on the clock". if i told someone to look at "2 o'clock" it means to their right, but not all the way completely
you mostly only hear 6 and 12 casually