Here's how you can download the App Lock app free for Android devices.
1. Go to the Google Play page for the free app App Lock.
2. Tap the Install button.
Here's a description of App Lock:
"Protect your installed applications using a password or pattern!
APPLock, Easy and Strong application lock tool !
More features coming soon.
* Protect installed apps using password or pattern
* Startup protect service / stop proctect service
* Lock incoming call
* Quick lock switch( Home Widget & status bar)
* Allow short exit，no need to unlock again."