I figured it out: The uno ring has no downward pointing collar. It is 'flat'. the unit (which looks like a collar) is in two parts, the ring and the collar. The collar goes under the shade, the ring tightens onto it. This was, in retrospect blindingly obvious except for the supposed breakage in the taxi, which threw me off completely. the ring seems to have moved THROUGH the shade, - Carbonaro-like!! No, i cannot see how on earth this could have happened, unless the person who gave it to my wife took it off for transportation and screwed the parts together wrongly, which she said she didnt??