The checkIn-checkOut plugin is a component for notepad++ to know who is busy to edit the file and avoid the overwrite of a shared file on network.
[*] Perform checkOut action for create the lock file with you username, who will prevent all other user who take ownership the file that you are to edit
[*] Perform checkIn action for free file and permit the modification by another user
When the user make the checkOut action, the plugin creates a temporary file in the same folder and with the same name but the .LOCK extension. ...