884de136_CVS_Command_Line_Reference__Action
[How to do it.] cd to the parent directory of your tree cvs tag -R -b labelname This will use the currently-checked-out versions of the files as they exist in your directory tree. The -b argument means that this tag is a "branch" tag, meaning that someone can check out a new tree based on this tag and do development. If you omit the -b, the label will be a "sticky" tag, meaning that someone won't be able to check in new changes under that label. See the notes on Labeling and Branching [Action] 
Label a tree for concurrent development
CVS Command Line Reference
Action