Some handset has wide display size which get difficult to handle with one hand, but if your device have one-handed operation features then you can easily handle your device with one hand in any point of time.
To activate one-handed operation, just go to settings then tap on display settings then click one-handed option, one handed operation will change the size and position some important apps like drilling keypad, in call button, massage keyboard, unlock pattern, calculator, so that you can easily handle your device.