If you have a specific app you want to lock so that others can't access it, the most secure way of doing so is with biometrics. While there are options to lock apps with either a PIN or pattern, these can easily be figured out with a simple glance over your shoulder. It's much more difficult for someone to crack your fingerprint ID, unless they chop off your finger, of course.
So that's why today I'm coming to you with this tutorial to lock your applications on Android using your fingerprint.