I have posted a 5-sided cube containing a set of 4 rungs in the "Odds and Ends" section of the BB forum. I am working on a boxcar that uses rungs rather than ladders. I started out making the individual rungs but found the amount of "weight" on the traincar to be more than I really wanted. I stripped everything out of the traincar in Blender except for one set of rungs and using screenshots of those rungs, put together a 5-sided cube of the rungs. This image contains one set of rungs and one rung cube. I can't tell the difference.
Each of my rungs contained 35 vertices, 140 for a set of 4 rungs and a whole lot of faces. The 4 sets of rungs, one on each corner of the boxcar, equals 560 vertices. The rung cube does it with 32 vertices for all 4 corners of the boxcar.
I thought someone else might find this helpful. Some traincars just don't look quite right with ladders when they actually need rungs. The rung cube can be added through NifSkope, or you can copy them to another diff file for the car you are working on. You would then need to make the appropriate adjustments to your alpha and adjust the uv map.