Keyboard shortcut to close "other" folder column?

I know you think the next thing I will ask is for you to open my beer AND pour it in my mouth (and maybe even swallow for me)... But is there a shortcut I am not seeing so that when I am on one column of a two column display, I can close the other column, as if I couldn't use the exercise of pressing a couple extra keys (Tab (if pref set) and Ctrl- W). Yeah, I guess you're right. Would you open a beer for me . . . . . --Chris

F6 toggles the dual file display by default, but you can change the hotkey to whatever you want via Settings > Customize Toolbars > Keys