Calculator Lock: Calculator is the best photo and video vault and file lock app for Android devices. If you want to create a secret folder for your photos, videos, and other files, then this app is the best choice. 

The app can be used in two ways: as a normal calculator and as a photo, video, and file lock. In the first case, you will be able to perform all the usual calculations and even do a bit of math. In the second case, you will be able to access your photos, videos, and files only with the help of the PIN that you set. 

The first thing that you need to know about this app is that it is a free app that is capable of hiding photos, videos, and files.