Tired of all those file lockers and vault applications that no longer work after Google's new Kitkat SD card policies?

Try SDcardLock.
Currently in Beta stage.
This app is simple and safe and uses no unwanted permissions. You can check for yourselves.

Link to the app : 
https://www.dropbox.com/s/gt6fqcf795ds7ov/SDcardLock.apk?dl=0

You MUST read this tutorial to learn how to use it.
Link to tutorial :https://www.dropbox.com/s/c1wo9ij2ifapb5u/tutorial.docx?dl=0