What type of joint did Leonardo da Vinci use in designs for flexible mechanical movement?

Leonardo da Vinci used a universal joint in designs requiring flexible mechanical movement.

A universal joint connects shafts whose axes meet at an angle, allowing rotary motion to pass through a changing direction. Its basic action is commonly associated with a cross-shaped intermediate piece, although later versions took many forms. The mechanism became important in machinery and vehicle drivetrains.

Leonardo investigated related joint and shaft arrangements while studying mechanical transmission. His notebooks contain early representations of mechanisms that can be understood as universal-joint principles. That does not mean he created the fully standardized modern automotive component; later engineers refined the geometry, materials, lubrication, and manufacturing methods.

The term is sometimes confused with a ball bearing. Bearings reduce friction between moving surfaces, whereas a universal joint transmits rotation through an angle. A dovetail joint is a woodworking connection, and a riveted joint is a fixed structural fastener.