Most recently, I was working with a student on the angles in a triangle. We started with a circle to show the angles all the way around, their sizes, and how they compare to each other. Then, I set my arms hand to elbow in an L shape. We worked on showing the sizes of various angles by moving my hand at 12-o'clock (90 degrees) to a position that would show the angle size when my other arm was at 9-o'clock (zero degrees). It worked very well.