Setup Bars
thingiverse
I've printed one of the most useful things from here: https://www.thingiverse.com/thing:1793172, along with these setup bars. If you're serious about it, then buying proper setup bars is a good idea, but these are lightweight, durable and super handy. They're definitely worth printing. Print one of them and check the dimensions - if you need to make any adjustments, I've uploaded the Fusion 360 archive so you can do that easily. My Makerbot z18 has a variation of 1/128 of an inch along the print, but that was good enough for my purposes. To learn how to use these together effectively, watch this video: https://youtu.be/VgpbUzfjDeQ?t=658.
With this file you will be able to print Setup Bars with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Setup Bars.