A simple printed case for the Arduino Nano V3. The bottom half has two rows for the bottom pins. The top design allows access to the reset pin through the center hole and visibility for the four onboard LEDs. The two halves fit together with simple friction and are held together with the help of the natural ridged pattern from fused filament printing.
I've only been able to print with PLA on a Printrbot Simple with the sizes in this model. The bottoms and sides are thin enough that the infill percentage doesn't make much difference. It's a relatively tight fit for the three Nano boards I had available, so I'm not certain if shrinkage with ABS would be an issue.