The lock has a hook, a locking finger and a latch. The locking finger is engaged with the hook and the latch when the lock is in the locked mode. The locking finger is disengaged from the hook and the latch when the lock is in the opened mode. The lock can be opened by a combination mechanism or by an overriding key mechanism. The combination mechanism has a button, and a plurality of dials and clutches to control the movement of the button. When the dials are set to a correct combination, the button can be moved to disengage the latch from the locking finger, allowing the locking finger to disengage from the hook. The key mechanism has a cylinder with a key slot to receive a key for rotating the cylinder to disengage the latch from the locking finger, allowing the locking finger to disengage from the hook.