Binding a keyboard shortcut to shut down I want to bind a gesture in BetterTouchTool to the shut down menu that is invoked by pressing the power button on my MacBook Air.

It's fairly simple to bind gestures to keyboard shortcuts, so what I'm really looking for is a way to bind a keyboard shortcut to the shut down menu. You can't use the power button in BetterTouchTool, so I need to bind it to a standard keyboard shortcut such as Command+Shift+S.
You don't need to map the power button, that menu is already mapped to control+eject



Other useful shutdown/restart/logoff key mappings are below which might be of interest too  

Prompt to save work and restart the Mac - Control+Command+Eject  

Prompt to save work and shutdown the Mac - Control+Option+Command+Eject  

Sleep - Command+Option+Eject  

Sleep displays - Shift+Control+Eject  

If the computer isn't responding and you need to force it to power off, you can hold down the power button for 6 seconds, you'll lose unsaved work though.  

These power shortcuts are listed on the apple support pages