The insert (13) is lockable opposite the ink fountain roller (8) fixed in position relative to the ink fountain (3). The insert is spaced from the roller to allow full inking between the side walls (4) of the ink fountain. The relevant interspace between a side wall (16) of the insert (13) and a side part (4) of the ink fountain is ink-tight at least in an area close to the ink fountain containing the maximum filling level. The side walls (16) of the insert protruding up at the side parts of the ink fountain each have a bearing supporting on the side part and fixed against lifting from the side wall.
