The fabled Skeleton Key; master of doorways.
Skeleton keys have been used for centuries in various paths of magic worldwide, to name a few;
Divination – Used as a symbol of opening the door to the other side.
Anchoring/Grounding – Used to Anchor a spell to a target or to ground the spellcaster.
Protective talisman for Travellers – Hung around the neck of the traveller to protect against misdirection and becoming lost
Road Opening – Used for the symbolic opening of doors and removal of astral blockages.
Deity Veneration – Corresponding to spirits such as Hecate, Eleggua, St Peter, Papa Legba etc.