atomarc is correct in all regards. Howver, my Chevy Duty window channels (5-6 years ago) came with the clips in place (3 on each side, I recall). Steele's and Jim Carter's did not. I had to pop-rivet them onto the channels I got from Jim Carter, because I could not get the attachment "tang" to hold (will use Chevy Duty's from now on).
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The clips keep the channel pushed towards the outside edge of the door. I cannot recall if I screwed the channels into the door frame. As I dimly recall, they either float or are held in place by a sheet-metal screw at the top and a larger sheet-metal screw from the outside edge of the door into the lower end of the channel (where a spring nut is attached). I might not remember this correctly and will see if I can find photos this evening.
I think you could get by without the clips but I would try to get them in.
Tim
