After a beer glass has been properly cleaned and allowed to dry, there is one more step to perform before serving a beer: a final rinse.
State-of-the-art draught service systems now have a rinser built into the draught tower base or mounted separately at the bar. Pressing an inverted glass down on the crossbar sprays cool and filtered water into the glass.
This helps to cool the glass to room temperature in case it’s still warm from washing. It also removes any residual rinse aid and conditions the surface of the glass for proper head formation.