Module bays represent a space or slot within a device in which a field-replaceable [module](./module.md) may be installed. A common example is that of a chassis-based switch such as the Cisco Nexus 9000 or Juniper EX9200. Modules in turn hold additional components that become available to the parent device.
!!! note
If you need to model child devices rather than modules, use a [device bay](./devicebay.md) instead.
Like most device components, module bays are instantiated automatically from [module bay templates](./modulebaytemplate.md) assigned to the selected device type when a device is created.