38mm x 25mm Red Fully Graded Slate Lath

These are typically coloured. This clearly identifies that the batten is graded. Graded is either visual or by machine. Machine grading is usually by a combination of lasers and camera scanners. A third party accreditation usually forms part of the factory process control. Waste is minimal with only a check for end splits that may occur post grading and cutting back to the nearest rafter.