One very rare thing I miss from Windows was the ease of being able to lock my machine when I walked away. Just by pressing Ctrl-Alt-Del, you could prevent anyone else using it in a jiffy.
Of course, this is also possible on Mac when working on different profiles but Locker makes it easy by adding a useful widget to your dashboard that prevents anyone else from using your computer. When you double click it, Locker locks your Mac - simple as that. It takes you straight to the Mac login window so it's really just a shortcut to using the fast switching menu item.
There's nothing more to it than that. It's completely free to use and prevents you worrying whether your keyboard or Mac is being tampered with while you go on that long overdue coffee break.
Simple and effective, Locker is the solution for anyone that wants to easily lock their Mac so that no one else can use while they're away.