Constructed of heavy duty aluminum and stainless steel hardware, Salsbury 3900 series high security free standing 4C mailboxes can be accessed from the front through one (1) easy opening master door panel. These units provide a convenient means of installing 4C horizontal mailboxes in locations where a wall mounted application is not desired or available. The 3900 series 4C free standing mailboxes are durable and corrosion resistant that can be used indoors or outdoors and feature a powder coated finish in aluminum, bronze, gold and sandstone. All mailbox doors include a heavy-duty cam lock with a dust/rain shield and includes three (3) keys. A compartment equivalent to two (2) 3.25 in. high standard mailbox doors is used for outgoing mail collection and is labeled "Outgoing Mail". The outgoing mail compartment includes a weather protection flap, mail slot and carrier access door, which includes the U.S.P.S master lock access door (lock installed by the U.S.P.S), and anti-fish plate on rear of mail slot to prevent tampering of outgoing mail. The 4C free standing unit include a U.S.P.S. approved 4C horizontal mailbox unit and matching enclosure. Ideal for apartments, condominiums, commercial buildings, residential developments, colleges, schools, private postal centers, corporate mail centers, military bases, government agencies and many other applications. Salsbury Industries is an ISO 9001: 2008 certified company and has excelled in the field of manufacturing since 1936.