A note that applies to this entry and to the other objects in the atlas that belong to initiatory traditions, the khatvanga, the yantra, consecrated implements generally.
What an object is, what it looks like, where it came from, what tradition uses it and what it is broadly for: all of this is public. It is in art history, in museum catalogues, in the traditions' own published literature, and describing it clearly is the point of an encyclopedia.
What is not published here: consecration formulae, the mantras attached to a specific implement, the sequence of a rite an implement is used in, or instruction that belongs to a transmission from a teacher. Those are withheld not because they are unavailable, much of it has been printed, in some cases by people who should not have printed it, but because availability is not clearance. The traditions concerned regard that material as passing person to person under conditions, and reproducing it here would take a decision that is not ours to take.
The practical effect is a limit on what these entries do. They will tell you what a vajra is and why it is held in the right hand. They will not tell you what to say while holding it. That gap is intentional and it is where it should be.