It's obvious: The stuff from Bernbaum locks onto the channel. In fact, the channel is removable. In fact, I can see now that the channel must be removed when I go to take the upper stainless trim off for polishing (and, the interior upper rail for rechroming). So that's what it's all about... The book says nothing about removing the regulator, or the upper weatherstripping channel, in order to get the rear window out. But, I don't see how one could do it otherwise. Dan