General contractor Tom Silva visits homeowner Christian Dierkes to help him secure a shaky newel post at the top of his stairway. Back in the loft, Tom, landscape contractor Roger Cook, plumbing and heating expert Richard Trethewey, and host Kevin O'Connor try to guess "What is it?" Then Richard makes a House call and finds a 50-year-old water heater that's dangerously close to the end of its life. Just in time, he replaces it with a new model designed to meet strict new national safety regulations.