Strictly speaking, the vent glass is held in place in the frame with glazing tape. I removed mine by spraying the edges with brake cleaner. The cleaner softened up the tape in minutes. Now the correct way to remove the whole unit is to remove the dividing bar. One truck I saw had the swivel rivet replaced with a small stainless bolt and two nuts. This was probably the result of a very clever shortcut to removing the vent assembly. If I have to remove mine again in the future, I will definitely go that route.
