Hinge

A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them.

[1] In Ancient Rome, hinges were called cardō and gave name to the goddess Cardea and the main street Cardo.

This name cardō lives on figuratively today as "the chief thing (on which something turns or depends)" in words such as cardinal.

The primary reason for using a hinge, rather than a simpler device such as a slide, is to prevent the separation of adjacent components.

A variety of self-actuating, self-locking hinges have been developed for spacecraft deployable structures such as solar array panels, synthetic aperture radar antennas, booms, radiators, etc.