The Border is the area of precisely definable width between the outside edge of a mat and the edge of the opening(s).
Apply Borders
Borders and the Dynamic Outsides
Borders: Apply Borders To Top/Bottom Layer: Properties Tab
Borders: Even Borders: Properties Tab
Borders: Lock Borders: Properties Tab
Border Properties
Border Size Fields: Properties Tab
Borders: Single Tab
Borders Toggle: Editor Tools
Single Tab Borders: Separate Left and Right Borders
Using the Borders
Apply Borders To: Editor Default Setting
Borders: Editor Default Setting
Border Sizes: Editor Default Setting
Borders Toggle: Editor Default Setting
Even Borders: Editor Default Setting
Lock Borders: Editor Default Setting