All areas are divided into four categories: a private domain, a public thoroughfare, an open area ("carmelit") and an exempt area. Transferring an object from a private domain to a public thoroughfare, or the reverse, is biblically forbidden. Transferring an object between an open area to a private domain or public thoroughfare is rabbinically prohibited. Transferring an object between an exempt area and any other domain is permissible. In addition, transferring an object for a distance of four cubits (or more) in a public thoroughfare or open area is forbidden.