Abstract: Cogging piece (1) for use when notching log constructional elements (2) to other log constructional elements (2) or to corresponding separate log constructional elements (9). The cogging piece is adapted to be attached to both ends of each log constructional element (2) and to the end of each end constructional element (9) that is adapted to face a cogged joint. The cogging piece (1) is provided with lateral (4at, 4bt, 7at, 7bt) and axial (5at, 5bt, 6at, 6bt) inclined surfaces that are adapted to rest against corresponding axial and lateral surfaces respectively of cogging pieces attached to below and/or above intersecting log constructional elements and end constructional elements. Thus an increasing vertical force on a wall leads to an increased axial contraction of the cogged joints in the same wall.