BTW: I tried to create half the model, but I could not apply a PD mirror pattern to the filleted shape. Is that a known issue perhaps?

Welcome. Please attach your FCStd file and your STL file for inspection.

Maybe like this:

Gottschi Some of the faces in your model are B-spline surfaces. There is also an issue with flipped normals. And even if adjoining faces are flat and seem to have parallel normals there are in fact small deviations. We don't know how this shape was created, but something must have gone seriously wr...

wildCAD wrote: ↑Sun Apr 21, 2024 3:50 pm FreeCAD does not have a colinear constraint

Actually it does: Sketcher_ConstrainTangent.

For a wall that is not rectangular you can create a shorter wall with the SM WB and then add a Pad. You should never create walls or flanges that intersect as that will make the model not unfoldable.

Your description is not very clear. Post the file from #1 so that we can get some idea of what you mean.

@Marco_T I'll update the page and also check the other TD pages. Thanks for reporting.

The classic solution is to create two extrusions and then use Cut (or Intersection? but I could not get that to work). See attached file.