Each puzzle piece must be uniquely shaped, to avoid one accidentally fitting into the wrong place. That means 1,000 different shapes for a 1,000-piece puzzle, each drawn by hand by workers. Before a puzzle is cut for the first time, each piece is sketched on a sheet of paper draped over the finished image.

— Here's How Those Hot Jigsaw Puzzles Are Made, Amie Tsang in The New York Times