A ruling pen is a drawing instrument for drawing with ink or with other drawing fluids.
A ruling pen contains ink in a slot between two flexible metal jaws, which are tapered to a point. It enables precise rendering of the thinnest lines. The line width can be adjusted by an adjustment screw connecting the jaws. The adjustment screw can optionally have a number dial.
- Cicale, Ann (2006). The Art & Craft of Hand Lettering. Sterling Publishing Company, Inc. p. 96. ISBN 978-1-57990-809-6.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
- Kirby, Richard Shelton (1918). The Fundamentals of Mechanical Drawing. J. Wiley & Sons, Inc. pp. 8–9.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>