Step 7: Protractor
Since we have a ruler, why not a protractor. I used the top of the tube to mark the angles. First, I traced the top of the tube onto a piece of paper then measured some angles around the circle. I included 0,30,45,60,90 around the circle to 360. You could also do 15o
increments if you want. I then set the tube down on the paper and marked with a pen each of the increments. Next I etched those marks with a sharp blade. To make the marks stand out I filled in the marks with a black felt pen.