Man those blue are bright. Love it.
OO

Ok, so does each knob have it's own little LED on/off switch? I just have this image of Olie with this jewelers screwdriver looking for this tiny little switch on the side of the knobs while on the dark stage.

That was funny. That is a good point though.
 
That's just one more thing you need to check before going live on stage.  
 
Have some spares battery inside, or somehow tap into that active nine volt battery as a backup. If I got lit knobs, that would been something I would address.

Altgrendel; if I recall correctly, the top portion of the knob twists to turn the LED on and off.

Actually Altgrednel is close. There is a set scew on the side that you use an allen wrench to turn the led on. BUT Dave is also correct in that you can just twist the top a little (it will unscrew completely. that's how you change the battery) and turn the light off too. I don't think this was Rogers intention but it is easier to turn the lights on and off.
 
OO

For the Record,
Roger changed the design a few times while developing my set. My knobs do not have the set screw on the side to turn the lites on or off. The only way is to turn the cap. Each blue LED requires 2 small watch batteries per knob.
Kris

Olie and Kris; thanks!!