JB LockNow is a free personalization app developed by iggy.dev for Android devices running on Android 4.1 (Jelly Bean) and above. With this app, you can easily lock your screen with just a swipe up from the Navigation Bar.

On Android 6.0 (Marshmallow), you can set JB LockNow as your default assist app by going to App Settings > Set Default Assist App > Assist App > JB LockNow after a long tap of the Home button. This app utilizes the BIND_DEVICE_ADMIN permission to provide the screen lock function.

One of the unique features of JB LockNow is that it allows you to replace Google search, enabling you to turn off the screen with the same gesture. It also supports shortcuts, giving you the ability to turn off the screen at any time. You can rest assured that your privacy is protected as you can disable the Google search from the configuration and remove the default apps.

Please note that when using this application, you will need to enable the device administrator (only to lock the screen). A prompt will appear when you start this app, and you will need to remove the device administrator when you uninstall this app.

If you're looking for a convenient and straightforward way to lock your screen, JB LockNow is a great option to consider.