Missing parts on my silver cat's axle???
I'm tearing my hair out trying to find out how the parking brake *works* on a Mark VII axle. It has one swapped in, 3.27, discs, trac-lok. I wanna say this little piece with a bolt threaded into it is supposed to...turn...get pushed in pulled out...something? It's right smack in between the two caliper mounting pin/bolts and has a very large but not deep hex head surrounding it, put a crescent wrench on that tried to turn it, didn't move so I assume I was wrong on that guess. But there is a bolt threaded into a round piece that has teeth around it but it's not a perfect circle, it's some odd shape, and it does rotate back and forth a little but trying to apply a little pressure doesn't seem to apply the caliper or anything. Again I have no idea what I'm looking at, I was just playing with it to see if I'd find something
The car's original cables are still there. I feel like I could fabricate something to hook it up...I just can't figure out what needs to move and where! 
Thanks!