Lenovo A1 Tablet - Manual (Page 7)

Manual Lock
If your IdeaPad Tablet A1-07 is powered on and you do not use it
temporarily, you can tap the "Power" button on its upper right to
dim the screen display down. The device will then enter the
standby mode and become locked.
How to Unlock
Once in the standby mode, tap the "Power" button on the upper
right of IdeaPad Tablet A1-07 to brighten the screen display back
up to normal level. You can also touch and slide the lock icon to
the right, following the on-screen instructions to unlock the
screen, as shown in the figure below: