think of it like a speed crank for a follow focus. gives you an up/down lever alternate to gripping the ring. just find a bolt with the right threads and put it in there
I find the nubbin pretty handy for crash zooms, when that shooting style is called for. Somewhere on the camera there's a little threaded hole for storing it when it's removed, but I can't for the life of me remember where that is.
The threaded hole is up front on the top handle column, below the mount point for the microphone holder. I take it off when I have the zoom set to servo control and put it back on when I use manual zoom.