What year is your truck?
Some years had a thin rubber piece, or plastic piece, which was wrapped around the bottom of the glass then the sash was crimp to the window, if that was what your asking.
If your trying to just attach the sash to he glass check your other sides placement,if it works correctly, place it on your glass the same way mark it with a sharpie marker take it to a glass shop and have them urethane it on for a few bucks.
I'd say buy a tube but it will go bad fast if you don't have plans for it last I checked It varies between 10 and 20 bucks a tube, Calking gun type.
some times you can find small tubes at parts houses.
BE SURE OF THE PLACEMENT that stuff is a nightmare to get off!!!