A technical pen is a specialized instrument used by an engineer, architect, or drafter to make lines of constant width for architectural, engineering, or technical drawings. It has been also generally called "rapidograph", although that particular name is officially a trademarked line of products made by German company Rotring, and by American manufacturer Chartpak, Inc. when they purchased the rights from Rotring to produce the pens in the USA under the Koh-I-Noor brand.