Flats are considered to be envelopes and postcards, and make up the majority of all mail. Because these items do not vary greatly in size, machines can easily sort them. Flats Sorting Machines are built so that they can only handle mail of a certain thickness and width.

The machine consists of two sections. The first is the "load section", where a computer and an operator determine where each piece of mail is headed. The computer will check to see if a letter has already been imprinted with a barcode or other machine-readable code at a previous sorting center. In some countries the computers are also capable of Optical Character Recognition. This allows the computer to read certain parts of the address such as the postal code. It then sprays a barcode onto the envelope that will be read at future sorting centers. This eliminates the need to check a piece of mail more than once.

The Load Section.  You can see the computer terminal where the mail is scanned. *

If there is no barcode already on the envelope or if the computer is unable to read the address, an operator will manually sort the letter. This person reads the postal code and then inputs it into the computer. The computer then sprays a barcode or other type of code on to the letter.

The Sort Section.  Each of the yellow baskets is a mail tray, where all the mail headed for the same destination is dropped. *

The second section of the machine is the "sorting section". This consists of a long row of approximately 40-50 trays. Each tray represents a certain postal code, and each piece of mail will be dropped into a tray that corresponds to the postal code in its address. The letters move along a conveyor that is controlled by the computer that read their addresses earlier. When a letter reaches the appropriate tray, the computer will tell the machine to drop it down. Mail can then be collected from the trays and delivered to the next destination.

A postal employee sorting mail with a barcode sorting machine. *

While many countries have adopted automated sorting systems like this, it is still not practical in some places. These are usually small countries that do not have a large volume of mail. In those countries most mail sorting is completely manual.

* The sorting machines pictured on this page represent only one type.  There are many different variations of these machines, and this is not necessarily the kind you may see at your post office.

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