right angle ruler
thingiverse
See http://objects.reprap.org/wiki/Development:Workshop_Tools for other tools. The tool is parametric and has metric markers every 1cm on it. One side is slanted to get 45°/135° and raised to align higher objects properly. Instructions PRT-file can be edited with the free Alibre Design express or 30 the full day trial. (e.g. to export other sizes and angles) Feel free to glue a paper-ruler from the next hardware shop onto it.
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.