Metal Disks on the Wall
It’s never fun when you’re simply walking around and bam – you suddenly hit your knees on a metal disk attached to the wall. Ouch! On close inspection, the OP realized that there was more than one disk and they ran the entire way down the wall.
What was the purpose of their existence? Turns out they are skateboard-prevention devices essentially meant to discourage skaters from using certain railings and walls. We guess it would be pretty effective but at the same time, it could potentially hurt innocent walkers, like it did in this case. Perhaps a little warning sign would help.