Often, if you want to customize Joomla module or article after another user you can see the "lock" icon near it.
And when you want to enter your module or article you would see the message:
Check-out failed with the following error: The user checking out does not match the user who checked out the item. You are not permitted to use that link to directly access that page (#102).
It creates discomfort, because you can't manage your website.
For what that function is in Joomla, if it creates such a discomfort? I'll try to explain. "Lock" is a very old function, the origins are come from Joomla 1.0. "Lock" was created to prevent double editing of the same Joomla module or article. Hot it is works? very simple, when one administrator open article, the "lock" is arises, and the other administrator can't edit this article now, only after saving.
But "lock" can appear in an other way, when somebody editing the module, and then don't use Joomla buttons like save or close, but press back on his browser. And what you can do now? The article is locked and you can't edit it! To know how to unlock Joomla module or article follow this simple steps:
Also Joomla allows you to Check in all unlock items on the website by one click.
Now all module are unlock and you continue working without a problem. Find more trick on Joomla tutorials section.