Hunting dog kennel

A friend of mine has three hunting dogs and he keeps them in specially built multi-dog kennel. His hunting dogs' kennel is one of the largest privately owned dog kennels that I have seen. I have seen larger kennels in dog boarding facilities and also in animal shelters but his is by far the biggest that I have ever seen in someone's backyard.
His kennel is made up of modular dog kennel panels and that means that he can create any shape and size custom dog kennel that he wants. The modular panels are constructed from all steel frames and eight gauge heavy duty 2"x4" welded wire mesh with the wire mesh being attached to the steel frames with the direct drill and weld method so that there are no protruding parts that could harm the dogs.

Each of his three hunting dogs has their own covered sleeping area where they also have their food and water bowls but they all three share a main play area that also has their toilet area off in one corner. The toilet area inside of their dog kennel is built like a square sandbox and is made out of wood. Since they are larger dogs their toilet area is about ten foot by ten foot. My friend told me that if you have smaller dogs or only one it isn't necessary to build such a large area they can use a four foot by four foot area. Then inside the square box my friend spread sand over the bottom of the enclosure and then over the sand he put crushed rock. He used a very small sized rock but he also told me that it is possible to use a larger size of about one inch and that the larger crushed rock is commonly used.