You can lock a repository document to prevent other users from making changes to it. Only you or a user with the Full permission on the document can check in changes to the document until you unlock it. Generally, you will release the lock when you check in the document.
Locked documents display a lock icon in the repository browser:
You can lock a document during check out (see Checking Documents Out of the Repository) by selecting the Lock before check out option, and remove the lock during check-in (see Checking Documents into the Repository) by selecting the Unlock after check in option.
If you have locked a document (or have the Full permission on a document locked by another user, you can unlock it. Unlocking a document version allows any user with the appropriate permissions to check in changes to it.
Using the List of Locks (see Managing Document Locks in the List of Locks).