tmims

Noticed a bit of brake fluid leaking from driver side frame holes on my 2001 Cherokee Limited that I bought about a month ago. I traced the leak to the line junction attached on top of rear axle. Input from master cylinder ok, output to left and right wheels ok, the junction on top has a hose that goes into the frame, that's where the fluid is coming from. What is the purpose of this line, is it just a bleed port, I don't really understand why it is there? At any rate it was not real tight so I tighned the nut about 1/2 turn? Any words of wisdom would be appreciated, I'll report back if my tighten effort has any impact.