So I was doing a little winter caching the other day. There was an old foot bridge over a channel that looked good for a hide. The bridge itself was blocked off and the approach ramp had been removed with the exception of the joists. I had the brilliant idea to descend between said joists. Turns out snow on a steep incline is kinda slippery. Had a touch time of it getting my footing. And when I finally did, I looked at the joists that I had been (slightly frantically) grabbing for support. Yeah, every 6 inches or so was a rusty nail sticking up menacingly. I had actually snagged my coat on one and got a small tear. Thankfully that was all that got damaged.
So the moral of the story is, look out for rusty nails. Those buggers can be anywhere!