Three-Piece Block - Assembly puzzle by Stewart Coffin (STC #38)

Three-Piece Block

Assembly puzzle by Stewart Coffin (STC #38)

Assemble the three pieces into the pyramid shape shown in the photo.

Three-Piece Block is one of Coffin's most recognizable designs. It's surprisingly difficult despite having only three pieces, due to the unusual shape of the assembly. I can recommend it highly to anyone with an interest in interlocking mechanical puzzles.

Coffin tells the interesting story of the origins of this puzzle:

"I dashed off the design of this simple puzzle in response to a request from a New York advertising agency, whose client, Citibank, wanted hundreds of them for use in some sort of sales promotion scheme. The base of it presumably resembles Citibank’s corporate logo. I also made some for general sales. What a surprise it was when friends started reporting it was one of their favorite puzzles, much more confusing than I had at first assumed."

Printing Instructions

Print one copy of coffin.three-piece-block.stl. This model uses snap joints so that the pieces can be printed without supports; for this particular puzzle, I recommend using a sturdy PLA filament (or something stronger, such as PLA+ or ABS) and/or reinforcing with glue, due to the fragile nature of some of the joints.

After you print it, first connect all the joints before attempting to solve the puzzle. Snap each male connector into a corresponding female connector (for example, the male connector labeled "A" should connect to the female connector with a matching "A" label on the interior).

The joints are designed to be tight, and depending on the printer and filament used, you may need to hammer them into place. If they come out too loose, a drop of superglue will make them more solid (in most cases this shouldn't be necessary, but unfortunately tolerances vary across printers and filaments). The snap joint concept is discussed further in this tutorial: Getting Started with Puzzle Printing.

For a slightly smaller version that uses less material, you can print coffin.three-piece-block-smaller.stl instead.

The Printable Puzzle Project

The Printable Puzzle Project aims to make available high-quality open-source models of many puzzle designs. All of our models are posted with the generous permission of their designers and are licensed for non-commercial use only. Anyone may print copies for their own personal use, but selling or otherwise monetizing them is not permitted, and puzzle designers retain all rights as copyright holders of their work.

Our puzzles are modeled using the open-source puzzlecad library. The .scad file is included with this model in case you want to modify any of its design parameters; more information on how to do this can be found in the PPP Puzzle Modeling tutorial.

About the Designer

Stewart Coffin has been called "the most outstanding designer and maker of interlocking puzzles that the world has ever seen". He is credited with over four hundred designs, has pioneered numerous ingenious puzzle forms, and has written extensively about puzzle design and craftsmanship. More information on Coffin, along with many other printable models of his designs, can be found on the Stewart Coffin Puzzles overview page.

Happy puzzling!