It looked like free three inch first slab cuts off of small logs. All of the not square planks, the kind of trash which will gather at every lumber mill. Mills generally allow folks to haul it off for free.
People without money are always cobbling something together with it.
Navajos heat hogans, and build horse pens with it.
My guess as to what the Russians were doing with it was making a shaded work spot next to that building which would reflect sunlight down into that spot and make it very hot on a summer day.
Around here folks also sometimes build shade like that. There's also a way to make old tires into a large area of shade so folks can work in the sun.