I found a big hole in the chicken run the other morning. I thought that filling the hole back in, and covering it with a cinder block would take care of it, but apparently it did not. The animal just dug right under the cinder block.
The side of the run, that shares a wall with the shed is the weak point. All the other sides have four feet of wire on the outside to prevent digging, but I could not get the wire under the shed.
So far so good. It helps me sleep at night.