Update: added a support-free version with the connector flush on the bottom.
As I could not find any vertical HSW holders for my folding ruler, this is my first upload. You also an empty insert from the original HSW model (e.g. insert-empty.stl).
There are no particular requirements on material or print settings, apart from the obvious need for support (organic/tree support seems to work nicely).
This should fit most standard rulers, but in case you need to modify width/height/depth, you can modify those parameters in the f3d file yourself.
The author remixed this model.