This notorious vertigo-inducing ledge on Yosemite’s Half Dome is 1700′ above the ground. Some climbers call it “walking the plank.” One described it as “almost perfectly flat, and as you cross – it gets narrower and the wall pushes you outwards, just enough to be extremely precarious at the most narrow part. You would typically have to face outward … as you side step across. Some people crawl or use their hands on the ledge instead of walking.” Hey, just a stroll in the park …