On my home brew battery unit I didn't make much effort to case up or insulate the battery can, so there's a large area of negative polarity covered by only the original heat shrink sleeve wrap. With the possibility of contact on metal objects in my pocket I've wired the negative can directly to the exposed metal part of the screw connector, instead of putting the switch in that part.
The switch goes from the least exposed positive stud to the pin in the middle of the connector. My construction method is to use a short stub of hot melt glue stick between the battery and connector - which makes gluing it all together very easy, and provides a flexible mount that isn't just asking to be snapped off, just gluing it together seals all the positive bits of the circuit.
