Snakes. Watch for snakes in the pile. And in the tie. I had a kid (about 13 at the time), boy from church come help me build a fence around spot I wanted for a garden. We set cross ties for corner posts, and was stretching 2x4 mesh wire. He was pulling near corner post and holding tight, I was hammering steeples, when this snake sticks his head about 6" out of a split in the post. That kid took off like a rocket. I nearly fell out from laughing. Wasn't a poisonous snake that time, but any kind of "unexpected" encounter with one will make you hurt yourself if not careful.