I made this so I could attach my Circuit Playground Express (case has a tripod attachment) to an Arduino Uno board. I printed on a Mk3s at 0.2mm layer height with no supports. I used M2.5 screws to attach the Arduino, they just eat into the plastic. Then I used a ¾"  ¼-20 size hex head bolt for the tripod attachment. You could also use this to attach an Arduino to anything with ¼" threads. Fusion file is included if you want to modify for different attachments.