Abstract: A coupling apparatus (12) for a rod (7), such as a coating rod or the rod of a metering rod, used in a paper or board machine or equivalent, in which apparatus, there is between a first coupling element (5) and a second coupling element (6) a coupling piece (4) the length of which is changeable in the axial direction for connecting the rod to an actuator (1), in which coupling piece (4) the first coupling element (5) and the second coupling element (6) have been coupled for conveying rotational force, and in which apparatus, there is arranged between the first and the second coupling element, around the coupling piece (4) a protecting part (2) which functions as a preload element, and that the apparatus is installed on one or both sides of the rod.