Einrasten

Einrasten is a German term used in engineering and everyday language to describe a mechanical action in which a component is guided into a position and held in place by a projecting feature engaging a recess or detent. The result is a kinematic lock that is often accompanied by a distinct tactile or audible cue, such as a click.

Common implementations include snap-fit joints in plastics, bayonet-style mounts, and latch mechanisms in furniture, automotive assemblies, and electrical connectors. In a snap-fit, deformable ribs or hooks deflect during insertion and snap into a locked position; in a bayonet mount, alignment and a quarter-turn lock the parts together. Release can require force in a specific direction or an explicit actuator.

Applications: Einrasten is used where quick, tool-free assembly is desired, and where parts must remain fixed during operation but be retrievable, such as securing panels, covers, connectors, or modular components.

Design considerations: tolerances, material properties, and surface finish influence how easily parts engage (retention force) and how they wear over time. Designers balance retention against ease of release, operating temperature, vibrations, and aging. Improper engagement can lead to partial locking or accidental disengagement.

Relation to other terms: Einrasten is often translated as snap in place, latch, or engage; related German terms include Rastung and Rastverbindung. In English, “snap-fit,” “latching,” or “audible click” describe similar ideas.