Jimmy Reeves, center, mechanic, hammers in a wedge Nov. 13, 2012 under the watchful eyes of Ross Cunningham, left, lock and dam equipment mechanic supervisor, and Greg Cox, right, chief of maintenance section, U.S. Army Corps of Engineers Nashville District. The wedge connects the new cylinder to the rack on the upper river wall machinery at Cheatham Lock, Ashland City, Tenn. Upper river valves fill the lock chamber to lake level and lower river valves lower it to tailwater level. (USACE photo by Fred Tucker)