numbered like PO boxes. In the United States, this service is called caller service, and the assigned number is called a caller number, although mail is typically addressed to "PO Box (caller number)." Security Each country has its own rules and regulations as to how one can retrieve mail at a PO Box. Some countries, such as the United States or the United Kingdom, may require one or more forms of identification. Not all countries offer locked PO Boxes. In the United States, two forms of identification are required when signing up for a PO Box; one of which must be a photo ID. By continent Many countries offer some type of PO Boxes for different uses. There are an increasing number of private companies that provide similar PO Box services to the official postal service privately under the guise of mail forwarding. Africa Cameroon Cameroon uses the PO Boxes in Kumba, Yaoundé, Duoala, Bamenda, and other provinces. Namibia In Namibia, PO boxes are the only form of mail delivery to private individuals. Even small settlements feature a block of PO boxes for rent. In Windhoek, capital and the only large town, blocks of PO boxes are scattered all over the city and not necessarily located at post offices but at shopping malls, in pedestrian zones or on public places. South Africa The South African Post Office has Post Boxes available for rent. These are usually attached to or close to a post office. In urban areas with PO Boxes for rent there also may be home delivery of mail. In rural areas Post Boxes are often compulsory as no street deliveries take place. In the areas for which there is no street delivery, Post Boxes are not charged for. Boxes and Street delivery postal codes may be the same in an area, or may differ. Private Bags are available for recipients of large mail volumes. Asia Hong Kong In Hong Kong, PO boxes are available in two different sizes. They are available in many post offices throughout the territory. Japan In Japan, PO boxes are available at most post office locations. There is no cost to rent a post office box as the box is provided to ease the effort to deliver postal items to regular customers. Therefore, renters must receive at least one postal item every day and expected to visit and retrieve mails regularly (daily, in principle)