A tube stop for cooperation with a tube and fin furnace wall and a horizontal buckstay which includes first and second generally parallel generally planar spaced plates, apparatus for attachment of the first and second generally parallel generally planar spaced plates to the associated tube wall. A U-shaped plate has first and second opposed generally planar generally parallel space side walls, the first and second side walls being respectively disposed in spaced relation generally parallel relationship to the first and second generally parallel generally planar spaced plates, apparatus for coupling the first and second walls of the U-shaped member respectively to the first and second generally parallel generally planar spaced plates, and apparatus for rigidly coupling the U-shaped plate to the to the associated horizontal buckstay.