[Targalid]

For what it is worth I have caught myself, more than once, installing the screw slightly off target. It is easy to have the retaining ring look vertical but be slightly to the side of the threaded tab, one way or the other, then run in the screw, tug on the ring and have it feel secure only to find the screw falling out because I missed the tab. I always, since I learned i was missing the tab, use a bright flashlight to insure that the threaded tab is in line with the screw hole in the retaining ring. More often than not, I am off target and have to rotate the ring one way or the other to line up the fixtures.