is it exactly what it sounds like?
to blend and balance pup sounds?

i cant find any good explaination anywhere, and the only diagrams i found were for bass.
Quote by WickedBeast666
Noooooooooooo how could this be! he at all the chocolate in the box
Oh well, now the empty shell of what used to be chocolaty goodness can contain a tasty guitar circuit.

speaking of my homemade pedal
the blend is just as you guessed. To blend the sound of the pickups.
The knob in the middle means both pups are on full. as you turn it one way, one pickup's volume stays full, and the other turns down. the opposite happens when you turn it the other way.

as for the balance, I'm not sure... I'm sure I've seen it before, but I think I may have heard it called something different or something...