Some yr. ago, a buddy called and said the Forest Svc. was enlarging a reservoir about five miles out of town, we could go up there and cut a bunch of spruce they wanted removed. We got both our trucks, his trailer, our saws, some lunch, beer for after the cutting to help us load up the wood, got up there, found a place to cut amongst the many other guys cutting already, iced the beer in the reservoir, started in. His chain went first. Then mine. Then another of his. Then another of mine. We finally got into a trunk enough to find square nails. This was up in Arapahoe Ntl Forest, no old cabins around or anything, the nails from long before the reservoir was built. Who knows. Doesn't take big metal to do the job. I hit some hogwire once, completely grown into the trunk with no outward sign. That was a bear: nowhere to move the bar to try another cut for many inches with hogwire. Well, that's what I discovered at least, up til the time I figured out what I was dealing with, since I was guessing it was barb wire.