Turn a C battery into a D with quarters

You need a D battery but all you've got laying around are C cells. Since C and D batteries are both 1.5 volts (they differ only in size and energy storage), you can build a makeshift D to C "adaptor" with a few regular, conductive, George Washington quarters. Just insert them into your gizmo as pictured and you're good to go.

via Lifehacker