Abstract: An exemplary ring lock generally includes a housing, a shackle, a lock cylinder, and a first frangible component. The shackle is movable relative to the housing between an open position and a closed position. The lock cylinder is operable to maintain the shackle in the closed position, and is selectively operable to permit movement of the shackle from the closed position to the open position. The first frangible component is configured to break in response to application of a first threshold torque to the lock cylinder. With the first frangible component broken, the lock cylinder is prevented from permitting movement of the shackle from the closed position to the open position.