<Table> <Tr> <Td> </Td> </Tr> <Tr> <Td> Rapidograph stylus parts . The head can be further disassembled . </Td> </Tr> </Table> <Tr> <Td> Rapidograph stylus parts . The head can be further disassembled . </Td> </Tr> <P> In most cases, the final drawings are drawn with ink, on either plastic or tracing paper . The pen is generally a Rapidograph - type technical pen, a marker pen that draws lines of consistent width (so - called steel marker pen). The pen has an ink container which contains a metal tube, inside which is a thin metal needle or wire, the soul . Ink is absorbed between the needle and the tube wall, preventing an excessive amount of ink from being released . The needle has a weight and by waving the pen back and forth the needle is released and the ink can run . Originally, the tank was filled from an ink bottle; newer pens use ink cartridges . </P> <P> Each line width has its own stylus . The line width is standardized: In Finland, the most commonly used set is 0.13 mm, 0.18 mm, 0.25 mm, 0.35 mm, 0.50 mm and 0.70 mm . Separate styli are used for tracing paper and plastic, because plastic requires a harder pen tip . To function well they require regular maintenance, the finest marker pens in particular . </P>

Drafting tool is used when drawing vertical lines