right angle ruler
thingiverse
For more tools, check out http://objects.reprap.org/wiki/Development:Workshop_Tools. The tool boasts metric markers at 1cm intervals and features a slanted side for 45°/135° angles and a raised edge to align higher objects properly. Edit the PRT-file using Alibre Design Express or take advantage of their 30-day trial for customization (e.g., exporting various sizes and angles). Alternatively, you can attach a paper ruler from your local hardware store.
Download Model from thingiverse
With this file you will be able to print right angle ruler 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 right angle ruler.