6° A flat ruler made out of copper, carrying seven copper pieces b (fig. 3), so called retainer triangles.

6° A flat ruler made out of copper, carrying seven copper pieces b (fig. 3), so called retainer triangles.

The strands (1a), (1b), (1c), (1d) are of flat cross section and result from cuts (2) formed in a plate constituting the filiform element and are positioned relative to one another so as to serve as a clip by elastic deformation.