This tutorial explains how to enable one handed operation on Samsung Galaxy Note 5, which will certainly prove handy in situations where you need to manipulate (dial a phone number, use apps, unlock your device...) your smartphone with a single hand.
Go to Settings > Device > Display > One-handed operation. Two options are available:
Reduce Screen Size - Triple tap on the Home button to reduce the size of your screen.
One -handed input - Adjust the size and position of the keyboard, call buttons, lock pattern and other input methods for single handed use.