Files created with OpenSCAD and most are available on thingiverse: https://www.thingiverse.com/TooAngel
Some models use the Deftone Stylus font from Ray Larabie (http://typodermicfonts.com/deftone-stylus-upgrade/)
- Threads: http://dkprojects.net/openscad-threads/
- duplo-marbelrun-lib and duplo-block-lib are from https://www.thingiverse.com/thing:159219
- duplo-block-lib derived from http://www.thingiverse.com/thing:1778