I'll try re-phrasing and use better terms. The riser bar rides on the regulator arms . The "bar" then is screwed to the bottom of the frame. The frame has an upper A's well as a lower section that surrounds the glass.
It's the actual type of connector that I'm inquiring about.
I think it's time I spend time learning to post a picture. Someone told me, "a picture is worth a 1000 word". I'm a slow learner........