Screenshotting using PrtScr in cwm?

[bsd]

So, this work for me in .cwmrc:

bind-key 4-F11    "bin/screenshot"

It would make more sense to use the dedicated PrtScr key,  but I 
can't work out what it's called; I've tried to brute force the name.  

Also, xev doesn't detect the keypress.