For an overview on creating, visualizing, and simulating mechanical constraints, including UniversalConstraint, see Mechanical Constraints. Also see Roblox Units to understand how Roblox units compare to metric units.
A UniversalConstraint ensures two axes on two assemblies remain perpendicular. Example applications include vehicle power transmission to the rear drive shafts, robotics, and more.
Orientations
Orientation of a universal's two attachments affects how it will move. To ensure it behaves correctly, the SecondaryAxis of the attachments, visualized by the orange arrows, should be perpendicular to each other. Note that a green L-shaped indicator appears when the axes are properly oriented.
Limits
Enabling the LimitsEnabled property exposes the MaxAngle limit to restrict tilt within a cone, as well as Restitution which defines the elasticity of the attachments when they reach the limit.