What to do when forgotton your security pattern?

Is this android? If so there should be a option there on the unlock screen somewhere to reset the lock pattern using your email login attached to that device.

If there is no option to do this then you may need to completely "factory reset" the device, this will delete everything on it though!!!

Factory data reset in Recovery mode

If your Android One is on, turn it off.

Press and hold the Volume up button and the Power button at the same time until the device turns on.

Press the Volume down button to select "Recovery mode." If you need to navigate to the "Recovery mode" option, use the Volume up button to move the arrow and the Volume down button to select it.

You’ll see an image of an Android robot with a red exclamation mark and the words "No command."

While holding down the Power button, press the Volume up button and release it.

Use the volume buttons to scroll to "wipe data/factory reset" and press the Power button to select it.

Choose to erase all user data. This may vary by device. For example:

Scroll down to "Yes - erase all user data" and press the Power button to select it.

When asked to "Wipe all user data?", select Yes.

Your Android One device will erase all of your data and restart with its factory settings.

https://support.google.com/android-one/a...

First, turn your tablet off. Then, power the tablet back up by holding down the volume (either + or - ) and power buttons simultaneously. Continue holding the volume button until the screen says "Booting tablet in recovery mode." This will give you a picture of an Android. Tap the android, and you will be given a screen with several options. Move between the options with the + and -, and select with the power button. Go to the option for Factory Data Reset and select it. Scroll down to `the Yes, and then the tablet will erase its memory back to factory settings. Once it has completed, select Reboot Tablet Normally. Be aware that this will erase all data on the tablet.