For my Openbox rc.xml configuration I frequently enlist the Super (Windows) key in creating hotkey combos. Since the Caps_Lock key is larger, better placed, and rarely used I transformed it into another Super modifier key. An added bonus is that I can preserve my hotkeys configuration on keyboards lacking a dedicated Super key (example: my old Thinkpad X31) plus the new Chromebooks have a dedicated Search key in the old Caps_Lock location that by default acts as a Super key under Linux.
xev is a neat utility run in the terminal that allows one to press keys and outputs the corresponding keycode. The Caps_Lock key is Keycode 66. Create/edit /home/USER/.xmodmap ...
! Clear the caps_lock key binding clear lock ! Convert caps_lock into a super key keycode 66 = Super_L add mod4 = Super_L
Test the new setting by running xmodmap ~/.xmodmap. Place the command in /home/USER/.xinitrc to auto-load when running startx.