By default all columns in your grade book are unlocked but if you'd like to avoid editing or erasing a column by mistake, tap and hold on the header and select this icon shown here
![](/images/idoceo4/lock_column.jpg)
A locked column will look like this and you will not be able to erase it or edit it unless you unlock it first
![](/images/idoceo4/locked_column.jpg)
Tap and hold on the header and select this icon to unlock the column
![](/images/idoceo4/unlock_column.jpg)