With metal ends material composite design two top layers made of longitudinal glass fibres absorb bending forces and ensure more rigidity than wooden rules no swelling with water contact resistant to chemicals joints play free wear free and dirt resistant joint with spring pin for constant tension tight 90 and 180 latching of all joints scale greywhite version deep embossed black scale in 1 mm increments red embossed tens scale redblack version deep embossed white scale in 1 m