On the Vumark Design site: https://library.vuforia.com/articles/Solution/Designing-a-VuMark-in-Adobe-Illustrator
The explanation of the Contour:
This layer shall only contain one closed path with 4-20 straight edges. Once you have placed your Border and Clear Space parts into their corresponding layers, you must use the Pen tool in Illustrator to draw a closed path along the invisible “line” that is formed where these two parts touch. This path must be placed in the VuMark-Contour layer.
I don't understand the term "straight edge". What does that mean, can someone clarify?