New FB -Lock Dates - How to prevent edits to specific packages and questions?

To allow attendees to edit their registration but prevent specific items from being edited on the form you'll want to:

1. Turn post-reg editing on (basic settings page)
2. Registration form →  Select the package or question you want to lock
3. Set prevent changes after date →  Save

Lock dates are great for guest passes, t-shirts, banquet choices, instructor requests or any item with a hard deadline. They allow you to only lock specific items on the registration form, preventing last-minute changes while still allowing attendees to update other items in their registration such classing, number or vehicle changes. 

If you want to allow an attendee to select an item, but then not change it later, use the lock feature and set the date to the day before the event opens to prevent changes after they initially answer the question. This will allow them to select that item the first time through the registration form, but then not update it after that.