An Adjustable Ruling Pen is a perfect tool with many purposes including ink drawing and for masking fluid application. It has an adjustable screw to control the line thickness of the fluid line pen.  It is nice for drawing thin lines for trees, grasses, small branches, rope, and other fine details.

The art ruling pen is made of stainless steel and plastic, so it is durable and long lasting.  To use it: Dip the tip of the art ruling pen into ink pot to collect ink. Place the pen on a perpendicular angle to the paper. Do the same for masking fluid or liquid frisket.