Unique Property
The Unique property of the SPListTemplate class gets a Boolean value that indicates whether the list definition or list template can only be used to create a list during site creation and cannot be used to create a list through the object model or user interface after the site template or definition is applied.
Property Value
true if the list definition or list template is used to create a list only during site creation; otherwise, false.
Remarks
The list template for the Web Part gallery, site template gallery, or list template gallery is an example of a definition or template that is used to create a list only during site creation.
A definition or template whose Unique property is set to true is hidden so that it does not appear as an option on the Create Page or on the Documents and Lists page.
A list template or definition that is unique can be used to create multiple lists during site creation.
Requirements
Platforms: Microsoft Windows Server 2003
Security: Code Access Security