Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:5503575.
Simple adapter that allows you to use AAA batteries in an AA application. Good for using old AAA batteries so you can maximize the energy use you can get out of them. It's a shame to let batteries just sit unused in a drawer because you need on size up.
This requires the use of brass paper fasteners that act as the conductor. The size does not matter much as long as they are at least half an inch long. They will be trimmed to 12mm or so in length.
Simply snip the fastener tabs to about 12mm or 1/2" in length, insert the paper fastener into the slot and use a toothpick, small screwdriver, or similar tool to fold the tabs over the central post to secure it into the adapter.