The V-Groove Interior Backup (black arrow) is where the blade backs up before initially plunging into the fallout on the inside cut of the V-Groove. 

Interior Cuts cut into the fallout of the V-Groove, not the matboard. 

Select the desired Cartridge Tab and then the V-Groove bevel type from the Current Bevel Type dropdown control before making adjustments.

• V-Groove

The V-Groove Interior Backup, which is part of the inside cut of the V-Groove, is displayed on the V-Groove Configuration Map and on the associated field as a black arrow.

Check against the Configuration Map of the V-Groove you are cutting to determine specifically which cuts are the Interior Backups.

Interior Cuts cut into the fallout of the V-Groove, not the matboard. 

The inside of the V-Groove cuts first in a clockwise direction. These are internal cuts, which cut into the V-Groove fallout.

The outside of the V-Groove cuts second in a counter-clockwise direction. These are external cuts, which cut into the matboard.

The Interior Backup is part of the first pass.

This is viewed from the front of the mat. If the Interior Backup plunges the blade too soon, it makes the interior backup too long on the inside cut of the V-Groove.

Decrease the Interior Backup.

The corners will now meet up properly.

When making adjustments, click either the minus or plus button (-/+) at the end of the desired field about five or six times in the direction indicated. Click OK and do a test cut. Check the results of the cut and continue making adjustments until the desired outcome is achieved.

This is viewed from the front of the mat. If the Interior Backup plunges the blade too late, it makes the interior backup too short on the inside cut of the V-Groove.

Increase the Interior Backup.

The corners will now meet up properly.

When making adjustments, click either the minus or plus button (-/+) at the end of the desired field about five or six times in the direction indicated. Click OK and do a test cut. Check the results of the cut and continue making adjustments until the desired outcome is achieved.

This is viewed from the front of the mat. For an Exterior Backup where the blade plunges into the matboard instead of the fallout of the V-Groove, see V-Groove Exterior Backup.