On my 54 Chevy 3100, the door glass has no frame, but moves down felted channels on each side. The glass is pressed into a window track on bottom edge that the regulator roller fits into. On mine, there is nothing on either end of the track to keep the roller in, it just doesn't go close to the ends for that to be a problem. Classic Parts has a good video on the door rubber installation (47-61).
