A tool for assisting the process of marking or cutting structures in a predefined manner, wherein the tool comprises: - a rod member having a longitudinal axis and - a plate member rotatably attached to the rod member, - an arm removably attached to the rod member and to the plate member, and where - the plate member is rotatably attached to the rod member by means of a structure (40, 40', 42, 42', 44, 80) comprising a joint (44, 42, 42', 40, 40') whereby - one or more magnetic or magnetizable structures (42, 42', 80) are configured to provide a magnetic force between the rod member and the plate member and, - one or more magnetic or magnetizable structures are configured to provide a magnetic force between the arm and the plate member, - the plate member is rotatably attached to the rod member by means of a pivot joint (40, 40', 42, 42', 44, 80) comprising a cylindrical pin member inserted into a corresponding receiving portion (42, 42') whereby the cylindrical pin member is at least partly surrounded by a plane structure made in a magnetic or magnetizable material, wherein the receiving portion (42, 42') is arranged and configured to be brought into contact with the plane structure, wherein the plane structure and the receiving portion (42, 42') are made in materials ensuring that the plane structure and the receiving portion (42, 42') are attracted to each other by magnetic attraction whereby further, the pin member is attached to the rod member, and the corresponding structure having a bore is provided in the plate member, characterised in that the plate member is provided with holes (40, 40') arranged along the longitudinal axis of the plate member and whereby additional holes (38, 38′, 38ʺ, 38′′′) are provided in the plate member, wherein the additional holes (38, 38′, 38ʺ, 38′′′) are provided symmetrically with respect to the longitudinal axis of the plate member. - a rod member having a longitudinal axis and - a plate member rotatably attached to the rod member, - an arm removably attached to the rod member and to the plate member, and where - the plate member is rotatably attached to the rod member by means of a structure (40, 40', 42, 42', 44, 80) comprising a joint (44, 42, 42', 40, 40') whereby - one or more magnetic or magnetizable structures (42, 42', 80) are configured to provide a magnetic force between the rod member and the plate member and, - one or more magnetic or magnetizable structures are configured to provide a magnetic force between the arm and the plate member, - one or more magnetic or magnetizable structures (42, 42', 80) are configured to provide a magnetic force between the rod member and the plate member and, - one or more magnetic or magnetizable structures are configured to provide a magnetic force between the arm and the plate member, - the plate member is rotatably attached to the rod member by means of a pivot joint (40, 40', 42, 42', 44, 80) comprising a cylindrical pin member inserted into a corresponding receiving portion (42, 42') whereby the cylindrical pin member is at least partly surrounded by a plane structure made in a magnetic or magnetizable material, wherein the receiving portion (42, 42') is arranged and configured to be brought into contact with the plane structure, wherein the plane structure and the receiving portion (42, 42') are made in materials ensuring that the plane structure and the receiving portion (42, 42') are attracted to each other by magnetic attraction whereby further, the pin member is attached to the rod member, and the corresponding structure having a bore is provided in the plate member,