This 3D model is a versatile electrolysis holder designed to hold graphite rods from AA and AAA batteries.

It features holes sized for 4mm rods and the other for 3mm rods both from AA and AAA batteries. Additionally, there is a 5mm hole at both the top and bottom of the holder, providing connectivity for further attachments.
The design ensures stable positioning of the rods while getting very close together to boost efficiency.
This could be used for a demonstration of electrolysis, a HHO gas generator or just because it looks cool.
Keeping the positive metal bit of a battery connected to the rod makes installation super easy as well as soldering.