Hang a large, well packed scoop of vanilla ice cream on the edge of a fountain glass or other tall drinking glass. Fill the glass 3/4 full with root beer. Set the fountain glass on a salad plate, underlining the glass for overflow. Serve floats with straws and parfait spoons. When you are ready to enjoy the floats, knock the ice cream into the root beer and watch it fizz up as the ice cream floats. Yummy! This is the simplest and my most favorite fountain drink!