I did mine initially with a very small mechanical inclinometer, a 4' spirit level, a carpenters square and a tape measure.
Then I went to a store that supplies machine shop tools and purchased a small digital inclinometer and that made double-checking the installatin a breeze. I still needed the square and level (used as a long straight edge) to ensure the frame member to which the EDC is mounted is actually parallel to the instrument panel.
All in all, it took me about 2 hours to ensure the frame was parallel to the instrument panel and to ensure I had the EDC mounting tabs perpendicular to the instrument panel's axis. This was in a completed aircraft so I had much "stuff" to work around during this process. Those who are mounting the EDC during the build process have a much easier life!
