A Solid is a mathematical object, which is defined and represented by its boundaries (BRep)
Solids are heavier to compute than meshes but they do not depend on topology and they are better for a Boolean workflow (Union, Intersection and Difference)
In Sverchok solids depend on FreeCAD to work (that depends on OpenCascade) because Blender does not provide a internal way of handling this kind of objects.
A python 3.7 FreeCAD is needed.
A Windows version can be found here https://github.com/sgrogan/FreeCAD/releases/tag/PY3.7-win A Linux version reachable with $sudo apt install libfreecad-python3-0.18
Then the path to the FreeCAD “bin” folder has to be placed in the Sverchok Preferences ->Extra-Nodes ->FreeCad-> TextField and click on Set Path. Then re-start Blender and it should be working.
For Windows it can be as D:\programs\conda-0.18.3\bin For Linux it can be as /usr/lib/freecad-python3/lib/
If you change the folder, copy the new path and click “Reset Path”.
Sverchok provides a special Solids Menu by pressing “Shift + S”