Use the Select Selection Borders command to add a border around the selection. This command is useful when you want to add a border around the selection, and then fill that border using the Flood Fill tool.
To change the shape-based anti-alias:
Choose Selections > Modify > Select Selection Borders to open the Select Selection Borders dialog.
Choose whether you want to add a selection border Inside, Outside, or on Both sides of the selection border.
Mark the Anti-alias check box if you want to smooth the edges of the selection border.
Enter the width of the border in pixels.
Click OK to add a selection border.
Adding or Removing a Color from a Selection
Changing the Feathering of a Selection
Cleaning up the Edges of a Selection