Step 7: Protractor

Picture of 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 15
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.