"Like tying a Windsor knot or brewing a perfect cup of coffee, knowing how to hang art on your wall is a hallmark of everyday style and nuts-and-bolts know-how. The where, what, and whys of hanging art are an overlooked, under-appreciated line of inquiry. Most of us simply wing it with a quick eyeball and a swing of the hammer. How hard can it be? we think. What can go wrong? The answer, of course, is plenty: crumbling plaster, ruined antique laths,...