Brother replaced the old lock on the inner side of our house door with a new one of the same size and type. Yesterday he had the key of the house door lock duplicated after I asked help from him. But the duplicate didn’t work. He might have thought that reproducing a key was the easiest way to solve the problem because only one was left and the other had been missing. Even the duplicate could do, I would feel worried about the safety of our belongings for someone who had found or stolen the lost key might open the door in our absence.