Disregard, I think I get it when I looked again--so the flat part I'm seeing inside your claw is the flathead which gets adjusted using a screwdriver, and the little knurled barrel on the outside just screws on. On mine it's completely rusted on so it essentially acts like a thumbscrew you can use to turn the shaft. That also means on 2 of my 3 bikes, those little barrels are actually missing, and with those 2, one of them is backwards (the 2nd Italian bike). Does it matter? Should it be reversed so the head faces the axle?