How to Lock MacBook Files
Every MacBook owner needs to know how to protect files and folders from accidental deletion or editing. By locking a file, you allow it to be opened and copied — but not changed, renamed, or sent to the Trash. Locked items appear in the Finder with a small padlock attached to the icon.
To lock or unlock a file, you have to have ownership of the file. But on a MacBook where you’ve configured only one administrator account, you should already have ownership.
If you’re considering changing the ownership of a system-owned file, don’t do it. You could throw a serious monkey wrench into your Lion system.
To lock a file, follow this procedure:
Display the Info dialog for the item.
Select the Locked check box to enable it.
The Locked check box is in the General section of the dialog.
Close the Info dialog to save your changes.