What would a door criminal steal? A door, of course, but specifically a hinged door. You know, the kind that swings open and shut? That's the kind of door 扉 means.

To protect your door, you get help from 飛び Ra (とびら). 飛び Ra is the flying (飛び) version of Ra, the Egyptian sun god. Whenever a criminal tries to steal your door, 飛び Ra flies out from behind it and blinds them with his sun-god brightness.