Leaky skylight; repairing a light switch

General contractor Tom Silva helps a homeowner replace a skylight that leaks water into the kitchen below. In the ASK THIS OLD HOUSE loft, Tom, host Kevin O'Connor, plumbing and heating expert Richard Trethewey and landscape contractor Roger Cook ask, "What is it?" Electrician Peg Preble shows Kevin how to troubleshoot and repair a faulty three-way light switch.