To facilitate the incorporation to a fitting object by making components nonseparable, and incorporate them to the fitting object in the state allowing the fine rotation of the whole in conjunction with the lock-free action of a sprag while blocking the slip off in the axial direction against the fitting object.

In a first stage, one circular section 85a of a holder 8 is force- inserted between an inner ring 2 and an outer ring 3, and the projection 83 of the circular section 85a is thrust in with a slight elastic deformation. Tapered chamfering is applied to the end edge of the projection 83 so that the projection 83 is easily thrust in. In a second stage, the side faces of the sprag 7 are kept in contact with the end faces of the inner and outer rings 2, 3, and one of the inner and outer rings 2, 3 is rotated in the direction of an arrow B. The sprag 7 is tilted in the free state by the frictional force of this rotation. If the holder 8 is thrust into the depth of the inner and outer rings 2, 3 at this time, it can be inserted.