There is nothing inside the crates. The open side of the crate is facing the shed/coop side. I'm guessing since the 2x4 is only about 50" long, there are only the 3 (about 4 pounds) hens, and the way that the bungee cord straps *tightly* to the top of the crates, that it's been stable like it is. I have to exert a bit of pressure to pull the cord down tightly to hook it to the crates.
However, if they did tip it over, I would either tie the crates to the sides of the shed/coop or replace them with wood supports. I'm trying to do all of this without wood wherever I can avoid it.
This was a nice read explaining and showing how you evolved into what you now have. So many great ideas and the reasoning behind them. Great pictures too! Nice job!
Just a note that if you cut the tails off the zip ties, it would look a lot nicer, but that's just aesthetics.
However, if they did tip it over, I would either tie the crates to the sides of the shed/coop or replace them with wood supports. I'm trying to do all of this without wood wherever I can avoid it.