If you are using Android Marshmallow, then you might be using fingerprint lock to protect your device. Fingerprint lock is a security feature that allows you to unlock your device by scanning your fingerprint. To use fingerprint lock in Android Marshmallow, first open the Settings app and select the Security option. Then, under the Security section, select Fingerprint Lock. Next, enter your finger into the scanner and press the unlock button. The device will start to scan your fingerprints and will ask you to enter a four-digit code. Once you have entered the code, the fingerprint lock will be enabled and you can use it to unlock your device.
