lockexampleThe little lock symbol next to an Article Title, or Menu title, Category Title, Module Title, means that someone has the item open for editing OR they had it open and closed the browser window or logged out of Joomla without closing the item.

checkinIf you have Administrator Rights, like Super User, you can click on the Check In button in the action list across the top. This Check In buton is on the top of Menu Items, Articles, Categories, Featured Articles, screens for individual Components and Modules. If you do not have Administrator Rights, you need to either contact that contributor and have them log into Joomla, open that article and close it properly or contact an Administrator.

A person with Administrator Rights can globally Check In all the items on the site by clicking on Sytstem -> Global Check In.  You can click on the checkbox at the top of the list which selects all of the items, then click on the Check In button at the top of the page