[ATL ZJ]

Its the spot where it is adjustable.

Cleric

That means it's aftermarket. Don't drive around with that jam nut not tightened, please. Not only will having that nut loose not preload the threads properly, the wiggle may eventually wear down at them to where there is always a little slack in the connection. Once that happens, you're looking at nasty deathwobble and shopping for another new trackbar.