This is a really important step because, if you leave your cake upright, it will fall in, or collapse, on itself. If it falls, you won't have the light and fluffy cake that you so crave. You see, this cake has a lot less flour than your typical cake. The egg whites are what help it to rise, and if they're not allowed to cool upside down, well, they just can't hold themselves up. I talked about placing the tube of the pan onto the neck of a bottle or a can. But some angel food cake pans come with little feet that help the pan to stand upside down on its own. This cake pan is one example.