Repositions
the UVs of the selected faces on the boundary of the 0 to 1 UV texture
space as they appear in the UV Texture Editor.
Edit UVs > Unitize > 
- Create new UV set
-
Turn this option on to
automatically create a new UV set on the object to hold the unitized UVs.
Enter a name for the new UV set in the UV Set name box.
