How to wire a 2 cell holder to a third battery?

[Goodman]

Hi all, 'Searched already for this but couldn't find anything...

So I'm looking to wire a third battery in series to the two AA cell holder/US2.0 combo that Tim just released. Would anyone please help me with ideas on how to do that? I know it's simple...

thanks

[beggarsoutpost]

I wired 9v snap to a single plugged it into the double and hot glued them end to end...Glued my mock up soundboard to the back of the single....