Originally had crates, thought they were small so went to stackables bins. They are sitting on top of the crates, yet for some reason my hens push them over after laying an egg. I watched the hens intentionally do this today.
The bins are plastic so I'm afraid if I screw them into the wall they'll crack. Here is a pic of what the bins look like. How would you make them more heavy so they can't tip them over?
They're not stacked and they don't have wheels, but this is basically what the bin looks like.
organizeeverything1_2180_2522367177 by StonesChickens, on Flickr
The bins are plastic so I'm afraid if I screw them into the wall they'll crack. Here is a pic of what the bins look like. How would you make them more heavy so they can't tip them over?
They're not stacked and they don't have wheels, but this is basically what the bin looks like.

organizeeverything1_2180_2522367177 by StonesChickens, on Flickr