In Genesis, Eden is guarded by a flaming sword guarded by two angels. Does anyone know what this means?

I try to take the Bible as literally as I can, but this one thing perplexes me. How can one sword be guarded by two angels? A sword can only be wielded by one person, or angel. Is the sword displayed somewhere and guarded? Or, is this just a parable? Is the sword a person, place, or just an idea of how one should live?