Abstract: A one-piece outlet tube for joining the flat bottom wall of a metal gutter with a vertical downspout is formed from an initially flat blank. A continuous flat support flange extends around the margin of the gutter outlet tube at its upper end and rests upon the gutter flat bottom wall adjacent to an opening provided in this wall to receive the outlet tube. Integral outwardly struck downwardly tapering lock lugs are formed on the four side walls of the outlet tube closely beneath the flat flange for secure locking engagement beneath the gutter flat bottom wall when the outlet tube is inserted downwardly through the opening of this wall. The outlet tube is sealed with the gutter flat bottom wall around its support flange.