What is the meaning of ivory key

An ivory key historically featured in old catch questions of the Fraternity and was worn as a jewel in certain Grand Lodges 1. In general Masonic symbolism, a key represents secrecy, wisdom, discretion, and access to hidden mysteries, as an article on The Square Magazine's website notes.

The emblem does not form part of the standard symbolism or ritual of the three degrees of Craft Masonry. It belongs instead to the additional degrees, serving as the symbolic jewel of the Fourth Degree (Secret Master) in the Ancient and Accepted Scottish Rite, as an article on Universal Freemasonry's website records. On the wards of this Scottish Rite jewel is the Hebrew letter zain. In the Southern Jurisdiction of that Rite, the Scottish Rite's own website notes that "The Ivory Key" is also used as the title for an introductory education course on its history, structure, and philosophy.