Shapes are created by the position and movement of dog, handler, and disc. And shapes can be created by the dog, the handler, and the placement of the disc. Shapes are a fact of disc dog freestyle.
When the dog leaves the handler for a catch, that tends to create a line. When the dog is away from the handler and moves across the field to make a catch, as in a Zig Zag or Around the World, that tends to create a Shape.