What compact drafting instrument did Leonardo da Vinci use to construct or copy proportional drawings?

Leonardo da Vinci used a proportional compass as a drafting instrument for constructing or copying drawings at different scales.

A proportional compass has two pairs of points joined by an adjustable central hinge. Moving the hinge changes the relationship between the distances measured by the two pairs of legs, allowing a user to transfer proportions.

Leonardo illustrated and studied versions of this instrument in his notebooks. Such a device was useful for architecture, geometry, mechanical design, and the enlargement or reduction of figures.

The instrument should not be confused with an ordinary magnetic compass, which indicates direction, or with a simple pair of dividers, which transfers equal distances. Leonardo’s proportional instrument belongs to the tradition of precision mathematical drawing tools.