FreeCAD: Making tools to make things, serrated locking joint.

Sometimes the best way to make a thing in FreeCAD is to first make a helper tool.

[@justinahrens1868]

Thanks for the great tutorial!

[@GnuReligion]

Am happy to have worked through this. Still, left in wonderment how anyone figures things out.
Noticed that Create Sketch from Part Design will force you to "create a body." Reference sketches really must be made from the Sketcher WB. There are subtleties in all CAD tools, but FreeCAD is a particularly dangerous minefield.
Will attempt parametric designs from the plain Part workbench more often. All those Bodies complicate things.
Oddly little attention to this video compared to your "Tom Sanladerer" reply.