Ye Olde Silkie pen, aka Silkieland, is a flimsy contraption along the lines of the chickery, where the hardware cloth folds out on the ground and is anchored by rocks. Like HW says, it’s more like a mobile home than a trailer – technically, it’s portable.
It’s a royal pain to move the thing, because it’s long and floppy. All the rocks need to be moved off, then all the grass that’s grown through the mesh needs to be tugged loose, then the whole rickety thing needs to be dragged sideways, the coop (full of grumbling chickens) needs to be moved, and the pen reattached to it, then the rocks replaced. And everything that just broke in the struggle needs to be patched up.
However, it’s all worth it to watch how excited the birds get when first released. Excitedly burbling, all of them scatter and burrow into the grass. They are so clearly experiencing great joy that I promptly forget how much it all sucked.