A pelican hook is a piece of nautical rigging hardware composed of a hinged link held closed by a circumferential link capable of being released under load. Small examples are held closed by hand while the retaining link is displaced while larger examples are hit with a hammer or sledge hammer to release. The asymmetric appearance of the two hinged pieces is similar in appearance to a pelican's beak. It is frequently used to secure ships' anchors and life raft canisters but has many other applications.
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Pelican hook Wikipedia(Text) CC BY-SA