On the 'Line Summary' screen, select a line you want mark as unusable. Tap the 'Unusable' button.
The 'Unusable Line' screen is displayed. Using the drop-down box.
Once the correct comment has been added, tap the 'Confirm' button.
A replacement contingency line is chosen. Tap the 'Ok' button.
The line has now been marked as unusable. Scroll to the bottom of the table.
The contingency line has now been added, marked with a 'C'.