The large zigzag triangle fits perfectly against the edges of the circle and can rotate freely due to its rounded corners. One of its corners is slightly wider than the other two and using the notch in the middle, it can be lined up with the degree indicators along the circle.
This tool has a few different options for drawing patterns. One side provides a smooth wave pattern, at the opposite side you will find a zigzag pattern, and the final outer side is a straight line. This straight side can be used to create an equilateral triangle by repeating it three times with a rotation of 120 degrees. This side also has two pen-stops that indicate the length of a line segment needed to draw a hexagon, which can be created by rotating the zigzag triangle six times by 60 degrees.
The inner sides have the same patterns in a smaller scale.
Figure 1. With the zigzag triangle you can create intriguing shapes and patterns.