Your iPhone must jailbroken and Cydia installed then you can use this tweak to unlock the iPhone using volume keys instead of using the “Slide to Unlock” option. You even don’t need to press the Home button to see the “Slide to Unlock”. Just press the up or down volume button of iPhone to unlock the iPhone and this will let you straight to the iPhone Home screen.
Step-1
Run Cydia from your iPhone and tap the “Search” tab.
Step-2
Type vunlock in the search bar.
Tap the search result, tap the “Install” and confirm button to install it.
When it finish the installation restart the springboard. Now you have installed and volume buttons are ready to unlock iPhone.
Try it, press the Power/Sleep button on the top of iPhone and then press the Up/Down volume button on the side of iPhone to unlock it.