Building blocks allow authorized users to create and design reusable configuration attributes which can then be applied to virtual contexts. The ANM also allows you to extract the configuration of an existing virtual context and tag it as a building block.

In many cases, the same configuration settings can be used in several virtual contexts (for example, it can offer the same service bundle to many customers). To avoid repeating virtual context configuration and testing each time you create a virtual context, you can create a building block of many configuration attributes that can be applied to virtual contexts as appropriate or as needed.

With building blocks, you can also create a variety of configurations that address customers' differing needs. The ability to customize configurations to customer needs also allows you to use network resources most efficiently.

This URL should help you:

http://www.cisco.com/en/US/docs/net_mgmt/application_networking_manager/1.2/user/guide/UG_building_blocks.html