In my case, today I have learned how to apply surface properties in Armed Assault. Specifically, how to apply surface properties to roadways on objects (such as, for example, a certain bridge from several posts ago).
"Roadway", in ArmA, doesn't mean a road, per se, but rather a 2-dimensional surface upon which you can walk or drive in-game. This includes floors in buildings, stairs, and, of course, roadways as normal people would think of them.
So, the Roadway LOD (Level Of Detail - essentially a "layer" of the model) normally only affects where you can walk on an object. Turns out that you can apply a texture to it. And attach a configuration file, that says "where texture X is applied, use these surface properties". Very nice little trick to have discovered!
Now my metal decking sounds like metal decking when you walk over it, rather than dirt (the default surface sound). Just gotta figure out what the roadway textures are that I need for the rest of my bits 'n' pieces.
Still, as I said above - today I learned something. And it was good to learn.