---
"mask" specifies the modifier keys that must be held to enable this action.
"key" specifies the key that is to be pressed. 
"keycode" may be specified instead of "key" if the key code is known but the key is not.
---
The mask section is optional. It can contain any number of the following values: 

A - Alt (mod1)
C - Control
S - Shift
1 - mod1
2 - mod2
3 - mod3
4 - mod4
5 - mod5

To see which keys are mapped to the various mask values, open a terminal window
and enter this command:

xmodmap -pm
---
"Action" is the action performed when this combination is pressed. 
---
See http://joewing.net/projects/jwm/config.shtml#keys for more details
---
