Thingiverse user and maker Don Schaefer created a 3D printable Binary Adding Machine that demonstrates how binary math works. His design was based on a larger, wooden version of the device created by Matthias Wandel. Schaefer created the smaller, 3D printed version for educational purposes, so teachers and students could have their own version of the larger wooden device. You can find out more about the project over on 3DPrint.com: http://3dprint.com/92406/3d-printed-binary-adding/