One useful tool that Android has in security settings is the Lock Pattern. Users can define their own lock pattern ‒ which is a combination of 4+ dots joined together by swiping a finger between them.

A pattern lock is used to protect devices from unauthorized access. It usually provides better protection than a simple PIN, as it cannot be derived using "social engineering". Still there are ways to "get around it", as you can find in the answers to Cannot unlock tablet as have no internet connection?

Pattern Lock
Pattern Lock (image courtesy