The Contour Hint point is used on the colour fill zone and brush lines; in other words, on Contour vectors. It allows you to control the line thickness and contour position. Also, if a contour is not animated correctly, you can use hints to correct the animation. For example, if a flag is not waving properly.
When adding a Contour Hint point, make sure to place it far enough away from the contour so you can see it snap to the contour.
Contour Hint points are yellow.