This is the .stl resulting from a Beginner Tutorial for OnShape. You can watch the video at: [OnShape Beginner Tutorial] (https://youtu.be/Br0Uj0VlNOw)

The supporting worksheet is at TeachersPayTeachers:

Reverse Engineering Worksheet

This object was creating using the web based CAD tool OnShape. OnShape has a free version that allows you to login and use al the CAD features. The only caveat is that you project is saved as a public file.

You can exprot the resulting STL for use in other pragram

You should download the accompanying worksheet:

https://www.teacherspayteachers.com/Product/Reverse-Engineering-Measurement-Worksheet-3817868