The technique is really easy, just line up the ruler along a straight edge and then use your pencil, or in my case, a bone folder, and run it along the ruler using your guided pencil mark. (The lighter blue card on the left is the template I was using to make a pocket envelope for a Baby Shower invitation.)
I have a Scor-Pal, but for small projects this new ruler works great. And, best of all, it was a great price, only $2.79 at Michael's. Try one out!