The telling
The lock is the one object below that works both ways: it holds the one within and keeps the one without waiting. Erlik's gate is told the same way.

The Underworld · Tamga
A closed padlock. The underworld hides not the door but the key.
The lock is the one object below that works both ways: it holds the one within and keeps the one without waiting. Erlik's gate is told the same way.