This is a remix of Arduino Case by 3DP. I've added a button to access the reset switch, removed excess material to make it slightly thinner, added a groove between the top case and lid to prevent any possible wobble, widen the tolerance to 0.35mm around ports, and did some cosmetic changes.

Print Settings

• .3mm layer height
• Infill 25%+

Assembly Hardware

• 4 M3 x 12mm screws for the bottom and top case
• 6 M3 x 16mm screws for hinges
• 3 M3 x 5mm screws for mounting Arduino

Inserting the breadboard is a tight fit. For easy installation line up the breadboard so that it's parallel to the opening and apply even pressure, and you shouldn't have to trim down the nubs on the breadboard.