A decision pen is a drawing instrument for drawing with ink or other drawing fluids. A decision pen contains ink in a slot between two flexible metal jaws, which are tapered at one point. It allows precise rendering of very fine lines. The width of the line can be adjusted by a set screw connecting the jaws. The adjustment screw may possibly have a digital dial.
Originally used for technical drawings in engineering and mapping with straight rules and French curves, it is now used for specific uses, such as framing or calligraphy. In the Soviet Union, dominant pens were widely used by women for eyebrow waxing, being used as tweezers.