This video shows you how to get the skull that is hidden in Bad Piggies Rise and Swine Level 2-31. The skull is located to the left of the starting grid. Place both boxing gloves next to the piggy, and put a spring on the pig’s left. This will help give him enough high to clear the steep wall next to him, protecting the skull.
If you have a different strategy for completing this level feel free to leave a comment below.