Chapter 6 Deploying Wireless Networks for FortiOS 5.0 : Using a FortiWiFi unit as a client : Use of client mode
  
Use of client mode
In client mode, the FortiWiFi unit connects to a remote WiFi access point to access other networks or the Internet. This is most useful when the FortiWiFi unit is in a location that does not have a wired infrastructure.
For example, in a warehouse where shipping and receiving are on opposite sides of the building, running cables might not be an option due to the warehouse environment. The FortiWiFi unit can support wired users using its Ethernet ports and can connect to another access point wirelessly as a client. This connects the wired users to the network using the 802.11 WiFi standard as a backbone.
Note that in client mode the FortiWiFi unit cannot operate as an AP. WiFi clients cannot see or connect to the FortiWifi unit in Client mode.
Figure 171: Fortinet unit in Client mode