Local historian Richard Duffy offers a look at Arlington's Spy Pond. Richard installs a new water line to the house. Tom installs the new pre-finished Brazilian chestnut flooring. Fiberglass gutters made to look like historic wood gutters are fabricated and installed. In the second half of the hour, on ASK THIS OLD HOUSE, Roger helps a homeowner plant a low-cost, low-maintenance privacy screen. Tommy demonstrates many uses for a speed square. Richard uses new technology to seal ductwork from the inside. And the guys ask, "What is it?"