This Whiteboard Buddy tool allows you to quickly and easily make squares, triangles, X's, hypens (-), =, circles, draw various straight lines in SAE and Metric, and measure and draw angles at 15 degree increments.
I wanted something quick and easy to make my checklists and other whiteboard/dry-erase board notes and drawings cleaner, so this is what I came up with as a first try. I've embedded magnets in the prints so the printer will pause at layer 19 for you to press in the magents I have linked here: https://amzn.to/3UQsH3V
IMPORTANT NOTE: The slots for these magnets are VERY tight. It will take some substantial pressure to get the magnets in place, but they do press in. If you prefer, you can use a razor blade to cut the edge of the slots slightly to make inserting the magnets easier, but it's not necessary.
Enjoy and let me know if you'd like to see any additions or revisions!