Technical pens were developed to draw long, continuous lines of specific, measured width, using genuine India ink. Because they are reliable, precise,  leak-free and perpetually filled in a way no dip pen could be, Rapidograph pens have all but replaced traditional ink line drawing instruments for manual mechanical drawing. Technical pens like Rapidograph use a feed mechanism with dozens of articulations to regulate the flow of ink, releasing the medium at a regular rate through a metal tube with a wire at the center. Technical pens can be used with different colors of ink, as long as the manufacturer indicates that the ink in question will not damage the pen.

The mechanism that makes possible the precision of technical pens also makes them delicate. The tips can be damaged by dropping or bending, and can wear down with heavy use, especially on mylar. Technical pens must be kept clean, and should be washed out thoroughly with cool water (never hot) at least every two weeks. A cleaning kit is available to flush water through the pen with a syringe. Bad clogs can be remedied with the manufacturer’s own cleaning fluid, which dissolves dry ink particles.