Ultra Precision Marking RulersDrawing an accurate line with a conventional ruler is difficult when you are looking from the side, which usually also means inaccurate. Ultra Precision Marking Rulers has tiny holes and slits at each graduation, enabling you to make a dot with a pencil or mark a line with accuracy to within a hairs breadth! The scale, being indented and etched in black, is easy to read. The surface is non reflecting and enables even tired eyes in poor light to mark