Depending upon the structure, I just use long screws in a wooden walled coop(no movement at all), into a piece of 2x4 mounted on the wall, and in my hoop coop I've got them fastened with zip ties(some movement allowed but very small) to the wire. Since very few saplings are perfectly straight and they have the bark on, it's fairly easy to fasten them in such a way that they do not roll.
