Releasable ratchet device, comprising: - a substantially cylindrical mandrel device comprising a grooved area on an outside surface circumferentially around the mandrel device; - a locking device being a substantially cylindrical locking ring with an axial through bore comprising locking grooves on the inner surface of the through bore; where the grooves of the grooved area and the locking grooves are provide with different angles, where the locking grooves are configured to be engaged with the grooved area of the mandrel device; where the releasable ratchet device, due to the different angles of the grooves of the grooved area and the locking grooves, may be configured to be in a locked state, in which axial movement between the mandrel device and the locking device is allowed in a first direction when the locking device is engaged with the mandrel device and movement between the mandrel device and the locking device is prevented in a second direction opposite of the first direction when the locking device is engaged with the mandrel device; the releasable ratchet device further comprises a releasing device configured to bring the releasable ratchet device to a released state, in which the locking device is pressed radially out from engagement with the mandrel device, where the locking device comprises an axial slit having a width (w), were the width (w) of the axial slit is larger in the released state than in the locked state, where axial movement between the mandrel device and the locking device is allowed in both the first direction and the second direction; characterized in that the mandrel device comprises an axial recess in the axial direction; the locking device comprises a fin protruding radially into the axial through bore and is provided in the axial recess in the mandrel device, such that the fin and the recess are forming a guiding device providing that axial movement between the mandrel device and the locking device is allowed, while rotational movement between the mandrel device and the locking device is prevented due to the engagement of the fin in the axial recess. - a substantially cylindrical mandrel device comprising a grooved area on an outside surface circumferentially around the mandrel device; - a locking device being a substantially cylindrical locking ring with an axial through bore comprising locking grooves on the inner surface of the through bore; where the grooves of the grooved area and the locking grooves are provide with different angles, where the locking grooves are configured to be engaged with the grooved area of the mandrel device; where the releasable ratchet device, due to the different angles of the grooves of the grooved area and the locking grooves, may be configured to be in a locked state, in which axial movement between the mandrel device and the locking device is allowed in a first direction when the locking device is engaged with the mandrel device and movement between the mandrel device and the locking device is prevented in a second direction opposite of the first direction when the locking device is engaged with the mandrel device; the releasable ratchet device further comprises a releasing device configured to bring the releasable ratchet device to a released state, in which the locking device is pressed radially out from engagement with the mandrel device, where the locking device comprises an axial slit having a width (w), were the width (w) of the axial slit is larger in the released state than in the locked state, where axial movement between the mandrel device and the locking device is allowed in both the first direction and the second direction; characterized in that the mandrel device comprises an axial recess in the axial direction; the locking device comprises a fin protruding radially into the axial through bore and is provided in the axial recess in the mandrel device, such that the fin and the recess are forming a guiding device providing that axial movement between the mandrel device and the locking device is allowed, while rotational movement between the mandrel device and the locking device is prevented due to the engagement of the fin in the axial recess.