Installing a pellet stove; gasoline-free lawn mowers

Plumbing and heating expert Richard Trethewey helps a homeowner install a pellet stove that will provide supplemental heat during the cold winter months. In the ASK THIS OLD HOUSE loft, landscape contractor Roger Cook shows host Kevin O'Connor several different types of lawn mowers that do not require gasoline. General contractor Tom Silva demonstrates how to install an old mortised lockset on a new door.