Here is a Tydol version that is on Ebay...
As Bob said, the large rolled lip (Tydol advertising against rear roll up side window facing out) fit over the edge of the roll up window... The window was then rolled up completely to "pinch" the clip... Most often wire clothes hangers would hang on the smaller hook.... (one could also hang 1 piece of clothing such as a coat or jacket on the hook, if they had no wire hangers)
These clips worked great as long as the window was rolled up completely...
I hope my explanation makes sense? My Grandma had such clips in her Rambler during the 1960s and we used them all the time...