Although the iPad is not a phone, and you're not likely to inadvertently call someone at 2 a.m., you still have sound reasons for locking an iPad:
You won’t inadvertently turn it on.
You keep prying eyes at bay.
You spare the battery some juice.
Apple makes locking the iPad a cinch.
In fact, you don’t need to do anything to lock the iPad; it happens automatically as long as you don’t touch the screen for a minute or two. You can also set the amount of time your iPad must be idle before it automatically locks.
Can’t wait? To lock the iPad immediately, press the Sleep/Wake button.
If you have an iPad with a Smart Cover or Smart Case (or any of the third-party equivalents), opening and closing the cover locks and unlocks your iPad, but the Smart Cover has the added advantage of awakening your iPad without making you drag the slider (though you may still have to enter a passcode).
Unlocking the iPad is easy, too. Here’s how:
Press the Sleep/Wake button or the Home button on the front of the screen.
Either way, the onscreen slider appears.
Drag the slider to the right with your finger.
Enter a passcode if you need to.