Create your default grid line within My Preferences.
Create your default grid line on the Grid Fields tab within My Preferences. You can choose to display their Grid Code or Grid Code Description for each Grid Field, depending on which version is more informational to you. The selections you make here will display as your default grid line when adding items to carts. If you want to ensure that you must manually select an option for your grids, leave the selection field on the right set to None.