The new window--run channels are more of a hassle. Begin with the most forward channel; leave the door part of the channel out so the window can move rearward a bit. Roll the window up, then reach through the inner door and feed the channel into its groove, pushing it up from the bottom until it’s about an inch above the sheetmetal. The channel slides better if you wet it. Next, roll the window down about halfway, making sure you don’t pinch the channel in the guide. Now you can easily pull the rest of the channel up, snap it into place, and trim it to fit. Roll up the window the rest of the way, and reach through the inner door to snap the lower part of the channel into the window guide. The door part of the channel is easy to install with the window rolled down.