A pantograph is a mechanical linkage device connected in a manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen. If a line drawing is traced by the first point, an identical, enlarged, or miniaturized copy will be drawn by a pen fixed to the other.

One arm of the pantograph contained a small pointer, while the other held a drawing implement such as a pen. When moving the pointer over a diagram, a copy of the diagram is drawn on another piece of paper. By changing the positions of the arms in the linkage between the pointer arm and drawing arm, the scale of the image produced can be changed.