You'll see a lot of these at the summit of Tai Shan. I think they're prayers that have been engraved onto padlocks which are then secured onto railings within temples. The largest collected are gathered together at the Jade Emperor Temple at the mountains summit where there is an engraver guy nearby.
I remember watching Michael Palin visit Tai Shan during his Full Circle travel series where he was in complete owe of these guys carrying all kinds of things across their backs up the mountain. It's bad enough climbing up carrying just a small day-pack but just imagine what it must be like for these guys. They must be very fit and I hope they're well paid for they're services. Just made me feel tied and inadequate just watching them!