Abstract: This seamer (10) with back-up assembly (50) includes a first table (30) supporting one of the workpieces W1, a second table (32) supporting the other of the workpieces W2, fingers (40, 42) clamping the workpieces to the table, and an improved back-up assembly (50) disposed between the first and second table (30, 32). The back-up assembly (50) includes an elongate back-up bar (52), a holder (54) carrying the back-up bar (52), a support (70) disposed in spaced relation from the holder (54), inflatable hoses (80, 82) operatively disposed between the holder (54) and the support (70), and a control system (88) inflating the hoses to adjust the elevation of the back-up bar (52) relative to the workpieces W1 and W2. The assembly (50) is slidingly removable as a unit to facilitate removal of the back-up bar (52).