Neusis ruler

A neusis ruler is a special tool used in classical geometry to solve complex problems involving precise constructions. It has a marked ruler with a sliding, pivoting arm or device that can be set at specific points and angles. By adjusting and locking these marks, it helps find intersections and solve problems like duplicating a cube or constructing certain angles, which are difficult with standard straightedges and compasses alone. Essentially, it's a versatile instrument combining measurement and movement, enabling the construction of geometric solutions that require more nuanced manipulation than traditional tools allow.