If you’ve ever been reading a trail write up and come across a phrase like “class-three bouldering,” you may have stopped and asked yourself, “What the hell does that mean?”

Well, it’s called the Welzenbach System.

“OK,” you say. “Now what the hell does that mean?”

Tom dug up a clear, short, and wonderful video from BackpackingVideos that sets the whole thing straight with footage from Joshua Tree to illustrate exactly what these terms mean.

Now feel free to throw ’em around when you want to intimidate other newbie hikers.

Via the venerable Two-Heel Drive .