A letter box, letterbox, letter plate, letter hole, mail slot or mailbox is a receptacle for receiving incoming mail at a private residence or business. For outgoing mail, Post boxes are often used for depositing the mail for collection, although some letter boxes are also capable of holding outgoing mail for a carrier to pick up. Letterboxes or mailboxes use the following primary designs: A slot in a wall or door through which mail is delivered (through-door delivery) A box attached directly to the building (direct-to-door delivery) A box mounted at or near the street (curbside delivery) A centralised mail delivery station consisting of individual mailboxes for an entire building also known as a "flock" throughout the South Island of New Zealand and parts of America. A centralised mail delivery station consisting of individual mailboxes for multiple recipients at multiple addresses in a particular neighborhood or community Styles and usage A "letter box", or "mail slot" in American and Canadian usage, is a slot, usually horizontal but sometimes vertical, about 30 cm by 5 cm (12 inches by 2 inches), cut through the middle or lower half of a front door. This style is almost universal in British homes and offices, but in the US is limited primarily to urban areas. Most are covered by a flap or seal on the outside for weatherproofing. The flap may be closed by gravity, or sprung to prevent it opening and closing noisily in the wind. Some letterboxes also have a second flap on the inside to provide further protection from the elements. There may also be a small cage or box mounted on the inside of the door to receive the delivered mail. Mail slots are limited to receiving incoming mail, as most have no provision for securing and protecting outgoing mail for pickup by the mail carrier. Sending mail from private addresses is possible in the UK, but Royal Mail usually charge an extra per-item fee for this service. Wall-mounted or attached mailboxes may also be used in place of mail slots, usually located close to the front door of the residence. They are known as "full-service" mailboxes when they have provisions for securing outgoing as well as incoming mail. Attached wall-mounted mailboxes are still used in older urban and suburban neighbourhoods in North America. They are especially common in urban and suburban areas of Canada, where the curbside mailbox is