Question: Sharpen a pencil on a rough concrete surface..
Option 0: Hold the pencil in one hand and angle the pencil to the side walk surface. Make the angle about thirty degrees.  Move the pencil back and forth until the wood is worn away a little.  Rotate the pencil in your and and repeat until pencil point is formed.
Option 1: Hold the pencil in one hand and angle the pencil to the side walk surface. Make the angle about thirty degrees.  Apply mineral oil to the side walk, then, move the pencil back and forth until the wood is worn away a little.  Rotate the pencil in your and and repeat until pencil point is formed.
Answer: 0