The ball tie bondage position is similar to the fetal position, where the bound person lays on one side with knees up against the chest and then the arms wrapped around the knees.
To secure someone in this position, the ankles and wrists are bound together to form the person into a "ball" shape. Once the person is secured in this position, they can be moved around and rolled onto their back or side to side. Bindings like this turn the body into a series of leverage points for consensual rough handling.