A fastening device for detachably fastening of an object, such as a wheelchair, thereto, the fastening device having a mountable base portion for mounting on an interior surface of a vehicle, the fastening device comprising an automatic locking retractor comprising a spindle rotatable around a transverse axis, the spindle supporting a tension strap connected at a captive end thereof to the spindle, the tension strap being arranged to be wound onto the spindle as the spindle rotates in a rewinding direction, and the tension strap being arranged to be unwound from the spindle as the spindle rotates in an unwinding direction opposite to the rewinding direction, the spindle being tensioned in the rewinding direction, the automatic locking retractor comprising an automatic locking mechanism for selectively locking the spindle, the automatic locking retractor having an unlocked mode in which the spindle of the automatic locking retractor is freely rotatable in both the rewinding direction and the unwinding direction, and a locked mode in which the spindle is prevented from rotating in the unwinding direction while being freely rotatable in the rewinding direction; and a manually operable lever connected to the automatic locking retractor and pivotally arranged around the transverse axis, characterized by the manually operable lever being biased by a biasing member to a neutral intermediate position when no manual force is applied thereto, the manually operable lever being manually rotatable from the intermediate position in a first direction to a tightening position thereby forcing the spindle when in the locked mode to rotate further in the rewinding direction and allow tightening of the tension strap, and the manually operable lever being manually rotatable from the intermediate position in a second direction opposite the first direction to a release position thereby unlocking the automatic locking retractor. an automatic locking retractor comprising a spindle rotatable around a transverse axis, the spindle supporting a tension strap connected at a captive end thereof to the spindle, the tension strap being arranged to be wound onto the spindle as the spindle rotates in a rewinding direction, and the tension strap being arranged to be unwound from the spindle as the spindle rotates in an unwinding direction opposite to the rewinding direction, the spindle being tensioned in the rewinding direction, the automatic locking retractor comprising an automatic locking mechanism for selectively locking the spindle, the automatic locking retractor having an unlocked mode in which the spindle of the automatic locking retractor is freely rotatable in both the rewinding direction and the unwinding direction, and a locked mode in which the spindle is prevented from rotating in the unwinding direction while being freely rotatable in the rewinding direction; and a manually operable lever connected to the automatic locking retractor and pivotally arranged around the transverse axis, characterized by the manually operable lever being biased by a biasing member to a neutral intermediate position when no manual force is applied thereto, the manually operable lever being manually rotatable from the intermediate position in a first direction to a tightening position thereby forcing the spindle when in the locked mode to rotate further in the rewinding direction and allow tightening of the tension strap, and the manually operable lever being manually rotatable from the intermediate position in a second direction opposite the first direction to a release position thereby unlocking the automatic locking retractor.