You can delete runs of tagged builds. If the selection of the runs that you are trying to delete contains tagged builds, then you get a warning and you have to confirm the action. Tagged builds will not get deleted if you perform a bulk delete (all or for a specific time span) by right clicking on the execution node.
To tag an existing build:
 in the 
                     			 Actions column of the build that you want to tag. 
                     		   
                  		   A confirmation dialog box displays.
 in the 
                     			 Actions column of the build that you want to tag. 
                     		   
                  		   A confirmation dialog box displays.