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Salsbury 4C Custom Horizontal Mailboxes - Front or Rear Loading

Model # 3700C-U

Made of heavy duty aluminum and stainless steel hardware, Salsbury 3700 series U.S.P.S. approved 4C custom horizontal mailboxes and fully integrated parcel lockers are available as front loading or rear loading units and are designed for indoor or outdoor use.  Front loading units include an outgoing mail compartment and the U.S.P.S. master lock access door.  The unit incorporates a solid closed back.  On rear loading units, the outgoing mail compartment is comprised of two (2) or three (3) fixed panels and there is no U.S.P.S. master lock access door.  The back of the unit incorporates heavy duty access door(s) with latches and continuous hinges.  Units are available in a standard powder coated aluminum, bronze, black or sandstone finish. Custom colors are available as an option upon request

I would like to view more detailed information (PDF File) for 4C Custom Horizontal Mailboxes.

I would like to use the 4C Mailbox Configurator to design my mailbox project.


More Information

4C Custom Horizontal Mailboxes - Front or Rear Loading
Following simple guidelines, custom units can be configured with a combination of varying sizes of mailbox doors and parcel locker doors.

1)  Determine the number of openings required using MB1, MB2, MB3 and MB4 mailbox doors and PL3, PL4, PL4.5, PL5 and PL6 parcel locker doors.

Custom 4C door size
Custom 4C parcel locker door size
Note 1:  MB1 is the smallest mailbox door available and MB4 is the largest mailbox door available.
Note 2:  PL3 is the smallest parcel locker door available and PL6 is the largest parcel locker door available.

2)  Configure your requirements into a double or single column unit.

Note 1:  Configure your requirements into a one wide (single column) or two (2) wide (double column) unit and into equivalent standard mailbox door heights. 
Note 2:  Mailboxes are only permitted in the top eleven (11) one high mailbox positions. Parcel lockers may be positioned anywhere. U.S.P.S. standard 4C requires a minimum of one parcel locker for every five (5) tenant compartments.  Parcel lockers are not required for installation sites with less than five (5) tenant compartments.
Note 3:  The outgoing mail compartment (OM2 and OM3) cannot be used for mail distribution and must be situated in the designated position.  See our standard units for illustrations of the designated position of the outgoing mail compartment (OM2 and OM3) in their respective heights.
Note 4:  Tenant locks in the top row of mailboxes must be no more than 67" above the finished floor and the bottorm shelf of the lowest row of mailboxes must be no less than 28" above the finished floor.  For front loading installations, the U.S.P.S. master arrow lock must be a minumum of 36" and a maximum of 48" above the finished floor.  The bottom shelf of parcel lockers must be at least 15" above the finished floor.

3)  Specify front or rear loading.

Contact us for rough opening dimensions and layout specifications.

4)  Specify Standard or Custom Color.

Contact us for more information about making your mailboxes a custom color.  Click to view custom colors for 4C Horizontal Mailboxes.


  • 4C Standard Horizontal Mailbox Video