The Free Universal Construction Kit is a 3D-printable set of adapters that allow you to connect 10 popular construction toy systems, including Lego, Duplo, Fischertechnik, Gears! Gears! Gears!, K'Nex, Krinkles (AKA Bristle Blocks/Stickle Bricks), Lincoln Logs, Tinkertoys, Zome, and Zoob.
F.A.T. Lab and Sy-Lab are pleased to present the Free Universal Construction Kit: a matrix of nearly 80 adapter bricks that enable complete interoperability between ten* popular children's construction toys. By allowing any piece to join to any other, the Kit encourages totally new forms of intercourse between otherwise closed systems enabling radically hybrid constructive play, the creation of previously impossible designs, and ultimately, more creative opportunities for kids. As with other grassroots interoperability remedies, the Free Universal Construction Kit implements proprietary protocols in order to provide a public service "unmet"or "unmeetable" by corporate interests. … The Free Universal Construction Kit comprises nearly 80 two-way adapters. These allow each of the different construction toys (Lego, Tinkertoy, Fischertechnik etc.) to interface with any of the other supported systems. Prior to modeling, the dimensions of the various toy connectors were reverse-engineered with an optical comparator fitted with a digital read-out accurate to less than one ten-thousandth of an inch (0.0001in., or 2.54 microns).
There's a poster to print out, too! It's all licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Originally introduced by Golan Levin and Shawn Sims in 2012, the Free Universal Construction Kit has since been exhibited at Ars Electronica, the Cooper Hewitt, Smithsonian Design Museum, and the Museum of Modern Art (MoMA) in New York in the Pirouette: Turning Points in Design show last year. And in the 14 years since its creation, 3D printer ownership has gone from a niche hobby to a major consumer category. 72,503 consumer printers were reportedly sold in 2013, according to Fast Company, but more than 1 million were sold in in the last quarter of 2025.
If there were intellectual property concerns, none seem to have materialized: no legal action or publicized complaining from any of the relevant companies is readily found. The Free Universal Construction Kit system (note that acronym) exemplifies the open-design movement, applying the principles of open-source software to the physical world. If it started with relatively simple projects such as this, its potential was made clear during the Covid pandemic and venture capitalists love it.
