I am not sure what dormant railway means. Anyway, use two facets to create quadrilateral shape, either by hand, or use perhaps use woo.triangulated.quadrilateral. If you also need some non-negligible thickness (and rounded quadrilateral -- from two partially overlapping fat facets -- is not good for you), use woo.triangulated.box.
If you provide more context for your need, I might be able to help you better.
First of all, thank you for your attention.
I'm doing a project that uses a box of 6x8x6 meters, filled by rail ballast. And later a wooden rail sleeper is inserted, and a cyclic vertical tension is applied to this wooden sleeper.
I'm using the Clumps to simulate them. And after the cyclic tension I will check how to apply it.
However, my question is about the railway sleeper. I'm trying to create a rectangular piece to simulate the dormant, but I still can not.
If you have any tips or solution I will be very grateful.