Missing front diff bolt?

[ree]

I developed a leak in the front diff. I took a closer look at it looks like there's a missing bolt!

Is this hole supposed to have a bolt in it? If so, what length and thread pitch? Should I use thread lock? How tight should it be?

http://www.eeaston.com/gallery/d/1700-2/DSC00805.JPG

http://www.eeaston.com/gallery/d/1701-2/DSC00806.JPG