Let's Make Robots!

WTF?

Variable Power Regulator Mystery DAMMITDAMMITDAMMIT!!!!

I suppose I shouldn't be complaining.  After all, the circuit works:

...and more or less this (the cap straddles the gutter on my board  but Fritzing is limited...)

There's no connection to pin 3, which is "output" supposedly.  Yet it works as a voltage controller-from 18v to 3v-12v (range.)