I have yet to build this, but I have an idea of what I would like to have. This is a diagram of what I would like to build to use for my breeding pens.
Each of the pens would be a lean to style pen much like what Redridge has shown. The are in the middle would be left open with a fence along the end to create an outdoor run what each pen could be given access to on a rotating basis. This would give me a chance to clean the pens while the birds were out playing, without worrying about dogs getting them.