What compass-like drafting instrument did Leonardo da Vinci design for drawing proportional enlargements?

Leonardo da Vinci designed a proportional compass for drawing proportional enlargements and reductions.

A proportional compass, also called a sector, has two arms joined at a pivot and marked with corresponding scales. By setting the pivot to a chosen ratio, a user can transfer measurements while keeping the relationship between the original and the copy consistent.

Leonardo studied and drew versions of this instrument for geometric construction, architecture, and technical design. The device could help artists and engineers reproduce a figure at a different scale without recalculating every measurement.

It is different from a magnetic compass, which indicates direction, and from ordinary dividers, which transfer distances without automatically applying a selected ratio. Leonardo's instrument belongs to the long history of precision drawing and proportional geometry.