Salsbury 4B+ standard horizontal 3600 series mailboxes have been approved to the required security upgrades of USPS-STD-4B+ and are ideal for apartments, condominiums, commercial buildings and many other applications. A front loading door panel swings on a continuous hinge. One mailbox opening is required for a master postal lock and cannot be used for mail distribution. Units include factory installed 3/4" W x 1/4" D trim and a solid rear cover. Custom engraved placards (related item #3667) are available as an option upon request.