Very often you will want to lock Clips and Sequences in order to make them more difficult to delete.
When you lock a clip in a bin, you are locking both the clip itself as well as the media it links to. Locking clips and media is not foolproof. Clips and media can be unlocked from within Media Composer as easily as they are locked. Additionally, someone who is determined can also very easily unlock media files at the Finder level without Media Composer even running.
When you lock a sequence in a bin, you are locking only the sequence itself. The media a sequence links to is not locked when the sequence is locked. See the Deleting Unused Media Files: Just Master Clips, just Precomputes, or both recipe that is earlier in this chapter for a discussion of how to lock the media files that a sequence is linked to.
It's also important to point out that locking a sequence in a bin does not prevent it from being edited. In other words, it will remain fully editable even...