I kept hearing a mysterious loud noise on the way home from work today. I crawled under to inspect when I got home and found this: http://www.feddishbasses.com/vw/arm.html  . Looks like I am missing a part.  Is this something I can fix myself or do I need some special tool to fix this?  Bonus question, if you can tell me all the parts I’m missing there you win the prize.

Thanks,
Bryan