Cutting holes is easy, lay out the hole, then drill a small hole in each corner then take a saber saw and cut it out. You will then need to reinforce the edges of the hole with some aluminum angle. If you look at the pictures attached you will see that I mounted the nest boxes to a piece of treated ply wood which I bolted to the steel wall supports. use 1/4 or 3/8 bolts with fender washers, Do not over tighten, You do not want to compress the wall . The cage wall I also anchored to the wall and ceiling supports. If you need more in info I will try to get some pictures of what you do not understand. Happy trails