Thank you for pics and explaination.. The side view and pic of slot in underside cleared up everythinhg. Other thread was useful also.
Like the glans ring idea but did not catch exactly how do they attache to the device. Is attachement point 2cm in to tube? Does it pivot? Pinch?...
I would practice on stock first. Dont know if stick would be fine bead or small detail. I imagine tig or mig are used more making these .