Bleeding Rear Drums

I recently changed the front pads and rotors on my 88 camaro IROC. I was also planning on bleeding the brakes to get rid of the softness that had built up. However, when i got under my car to find the bleeder on the rear drums, i notices that the valve is recessed into a metal plate. There is not way to get a wrench or socket around it in order to loosen it. What is the deal with that?