I am hampered by my ignorance, and the walls are closing in

Many thanks, Paul
Code: Select all
OS: Ubuntu 20.04.4 LTS (ubuntu:GNOME/ubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.28909 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 2084652)
Hash: 20846523c9d8219ec0fe33c499a64e700d2266b6
Python 3.9.12, Qt 5.12.9, Coin 4.0.0, OCC 7.5.3
Locale: English/United States (en_US)
Installed mods:
* LCInterlocking
* kicadStepUpMod 10.12.4
* Lithophane
* lattice2 1.0.0
* Defeaturing
* Manipulator
* fasteners 0.3.41
* sheetmetal 0.2.49
* Assembly4
* Curves
* POV-Ray-Rendering
* 3DfindIT 1.2.0