1. The key was as important as it looked; it was the instrument which kept the mysteries of the lumber-room secure from unauthorised intrusion, which opened a way only for aunts and such-like privileged persons. (Google)
2. Lumber room where the objects belonging to the tenants are stored is a model of Communal Apartment. (Google)
3. Apart from that, the lumber room is primary used as broom closet (e.g. a vacuum cleaner, brooms, a laundry racks, ... can be found here). (Google)