mattwj2002 noted in #reprap on 2012-03-19 that there were no printable checkers on Thingiverse, so I created a printable, stackable, mostly parameteric checker with a crown on one side. It will require good bridging. The bottom can either have a flat or domed indentation. ZGerman contributed the SCAD code for the ridges.It needs a little more work to finish paramterization.Download the STL or (better) download the OpenSCAD file, render in OpenSCAD, slice, and print.