You first assemble the puzzle and then experience the magic. When complete, use the Scratch Off tool to begin scratching the top layer. As you Scratch, the image will disappear as if the they are changing before your eyes! Experience the amazing world of Harry Potter. But don’t worry about the original puzzle image being scratched away. When scratching is complete, you can turn the puzzle over, and the original re-appears! This patented Scratch Puzzle comes with a scratch tool and brush. Total Scratch time is an enjoyable 3-4 hours of fun as you perfect each piece, and see the change before your eyes. The puzzle measures 24” x 18” with 500 pcs.