I first made one of these for one of those situations where I needed to hurry up and make it just to finish what I was working on at the time. The idea was originally inspired by a similar device that I found on an old geometry template that I had for drawing small polygons, but I modified this version to be better suited to woodworking. It has proved to be incredibly useful to me, and I hope that it will be for you as well.

Different reference lines can easily be added to it by using a little bit of clever geometry; I have thus far only created versions that contain divisions of the circle based on 60 and 90 degrees, because these are the most common angles for me, but I would also like to make a 72 degree version for aiding in pentagonal constructions. Once you start playing with this, you quickly realize that it can take the place of a protractor in many cases. Well, this video is almost finished uploading, so I hope that you enjoy, and thanks for your time spent watching.

Oh, one more thing: I've been using royalty-free music by Kevin MacLeod quite a bit now. After experiencing a few petty copyright snags (which are for the most part absurd and do not actually protect the rights or property of the creators of original content), I have found a treasure trove of good music in this guy. I usually choose subtle and non-distracting scores for my videos, but some of his music is downright beautiful. I regret that my amateur editing does not do the score justice. I advise you to check him out, so here is the link:

Music: Lasting Hope by Kevin MacLeod:
http://incompetech.com/