506 is inside of 507. You can see the tip of 506 sticking out of the end of 507 in your pic. Simply push 506 through 507 by pushing what you see inside of 507 which IS 506. It might feel stuck because 508 is is attached on the outer diameter of 506 which is part of the ratcheting system that holds it in place and won't let it back out, but it will push through. Make sure that when you reinstall it, that you get a couple of clicks from 506 when reassembling it before you reattach to the car.