Symbol 1656 from ISO 7000 - Title/Meaning: Lock 
Function/description: To identify the locking control. To indicate that a control is locked. To indicate that the function cannot be changed or adjusted because its operation is locked. To identify the location of a lock.
Own work using: iso.org/obp/graphics/grs/4f80510c-684a-485b-9e28-9e533f3151ae 200.png
Vectorization:  Mrmw