Newbie - Is someone in here?

Sometimes bathroom stalls in China don't have doors on them. Though this may seem shocking to some, it's quite convenient when faced with the dilemma of whether to push the door open to potential stall going-ons, or not. But for those more uncertain times, when you are blocked by those troublesome stall doors, here is a Mandarin Chinese lesson that will help you to rouse any occupants before you waltz in to do your business.