Abstract: Device locking systems, lock trees, and lockout methods are described according to some aspects. In one aspect, a device locking system includes a lock system configurable into a first configuration to lock a device to be secured and a second configuration wherein the lock system is configured to be attached to or removed from the device, wherein the lock system is configured to be locked into the first configuration at a desired moment in time by at least one lock, and circuitry configured to generate an alarm responsive to a change of the configuration of the lock system from the first configuration to the second configuration.