On my 110 you drill 2 holes in the spinner back plate and the bolt heads fit in these holes. This keeps the spinner back plate from turning. If it is a Tru-Turn the knurls on the back plate hold the prop in place (wooden props). The tight fit on the spinner into the back plate holds the spinner. I have drill the back plate groove and put a small piece of music wire in it and notched the spinner to fit over it.