Checking out a File tells the system and other users that you are working on the File. You can check out a File in 'exclusive' or 'non-exclusive' mode. Exclusive check out means no one else can make changes to the File until you check it in. Non-exclusive check out means someone else can also check out the File in a non-exclusive mode and edit it. If someone else checks in a File while you are working on it you will be notified. For instance, if you have a version 1.3 of a File and some one checks in a version 1.4, you will be notified that you have an older version.

To check out Files:

Go to your project and click on the Files link from the left panel
From the actions drop-down of the File click on Checkout.
Pick the mode - Exclusive - Yes/No.
Select the appropriate option and then click on Submit
The File will display the version number and the user who has checked it out.
If checked out in exclusive mode, it will display an X next to it.

After check-out, you can keep this copy on your personal computer and make changes to it and then check it back in. When you can exclusively checked out the File, no other user can check this out till you either revert back or checkin a new File.

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