yes, its for that.
you will need to first assemble the glass with its rubber on it and a thin nylon rope in the lip of the gasket, the putty is knead into a rope then applied to the frame where the glass goes.
The glass it put on and the rope is then used to pull the rubber over the frame lip. the putty will squish and seal it tight.
for help on google, lookup how to install old mercedes benz rear glass