The Trick Court Painters Use

Why do court painters never get trapped in the middle? Watching them, it looks impossible. They stand in one spot, paint a circle, then keep spreading outward. The more they paint, the more sealed in they seem. By the end, there's only one tiny gap left,

and if they step wrong once, they'd instantly ruin the fresh paint. But here's the trick. As they near the end, they keep painting As they near the end, they keep painting while slowly backing up to control the final opening.