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.

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.