A build can be "pinned" to prevent it from being removed when a clean-up procedure is executed, as stipulated by the clean-up policy.
There are several ways to pin/unpin a build :
using the Build Results page, the Build Action drop-down menu
on the Overview tab of the Build Configuration Home Page using the pin iconThe Pin/Unpin build dialog also allows you to tag the build.
If the build has snapshot dependencies, the Apply to all snapshot dependencies box appears. Checking the box will apply the actions (pinning/unpinning, adding / removing tags) to all dependency builds of the current one.
Concepts: Clean-up policy