no longer using an outdoor pen made from pallet collars and I would not recommend using them.
Rialto got injured twice, getting his nails caught in the hinges, and even when not ripping out his nails, his endless obsession with the hinges seemed to wear him out.
I have R now in outdoor raised bed which has dove tail joints (no hinges) and he is doing so much better - new growth lines at 10 + years of age are starting to show