Prevent a recorder thumb rest from sliding

I play traditional music on the recorder. I found that my thumb rest slid up the recorder and I was looking for a way to hold it in place. First I tried making a whole thumb rest out of sugru - very ergonomic but bright red as that's all I had at the time. Then when I got some black, I tried a blob of sugru above another thumb rest to stop it slipping upwards. They both work perfectly.

Vicky from Norwich, UK