The instrument consists of a rectangular glass panel with a semicircular protractor etched onto it. Graduated semi-circle divided quadrantally in degrees. The protractor's inner scale is marked from 8 to 0 to 8 by 0.25; the outer scale 90-0-90 by 1 degree. There are two inscriptions along the bottom edge: 'The Radiograph.' and 'H. Hughes & Son, London'. There is also a small hole at the centre for marking position.