Couldn't find anything in the documentation.

Cheers

I think rods are a way for FEM to handle lines/wires
FEM can handle several geometry types 0D (particle), 1D (rod), 2D (shell) and 3d (solid), each of them has it's own Material Property Parameters DOP, up until 18.5 I guess not all of them were exposed, but since they are now on Hybrid object I'd assume they would work now
so while I haven't tried I'd assume that particle properties are for isolated points, rod for lines, shell for poly and solid for tets

thank you Tamte